User equipment coordination for sidelink

ABSTRACT

Methods, systems, and devices for wireless communications are described. A user equipment (UE) may receive, from another UE, a coordination message that includes resource information (e.g., a preference status) for communication resources. The UE receiving the coordination message may determine a status of one or more resources based on the resource information, an intended recipient of the coordination message (e.g., based on a destination identifier of the coordination message), or a communication connection associated with the one or more resources. The status may indicate that a respective resource of the one or more resources is available, reserved, preferred, or non-preferred, or some combination thereof. In some examples, the one or more resources may be for a sidelink connection or a unicast connection. The receiving UE may utilize the determined status to select one or more resources for a sidelink transmission.

CROSS REFERENCE

The present application for patent is a Continuation of U.S. patentapplication Ser. No. 17/313,897 by SARKIS et al., entitled “USEREQUIPMENT COORDINATION FOR SIDELINK” filed May 6, 2021, assigned to theassignee hereof, and expressly incorporated by reference in its entiretyherein.

FIELD OF TECHNOLOGY

The following relates to wireless communications, including userequipment (UE) coordination for sidelink.

BACKGROUND

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., time, frequency, and power). Examples of suchmultiple-access systems include fourth generation (4G) systems such asLong Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, orLTE-A Pro systems, and fifth generation (5G) systems which may bereferred to as New Radio (NR) systems. These systems may employtechnologies such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal FDMA (OFDMA), or discrete Fourier transform spread orthogonalfrequency division multiplexing (DFT-S-OFDM). A wireless multiple-accesscommunications system may include one or more base stations or one ormore network access nodes, each simultaneously supporting communicationfor multiple communication devices, which may be otherwise known as userequipment (UE).

Some wireless communication systems may support sidelink communicationsbetween wireless devices. For example, a UE may communicate with otherUEs via one or more sidelink connections. In some examples, the UE maydetermine resources to use for sidelink communications with the otherUEs based on whether the resources are occupied (e.g., reserved by othersidelink UEs) or available.

SUMMARY

The described techniques relate to improved methods, systems, devices,and apparatuses that support user equipment (UE) coordination forsidelink. Generally, the described techniques provide for a UE toreceive, from another UE, a coordination message that includescoordination information for resources to be used in sidelinkcommunications and determine or otherwise identify a status of one ormore of the resources, the status indicating whether a respectiveresource is preferred, non-preferred, available, or reserved. Forexample, the coordination information may indicate a preference statusfor each of the one or more resources, such as an indication that aresource is preferred or non-preferred, and the UE may identify thestatus based on the indicated preference status. Additionally, oralternatively, the UE may determine the status based on whether the UEis the intended recipient of the coordination message; if the UE is notthe intended recipient, the UE may determine that the status of the oneor more resources is non-preferred, while if the UE is the intendedrecipient, the UE may determine that the status of the one or moreresources is preferred (or vice versa). The UE may utilize thedetermined status(es) to select one or more resources for a sidelinktransmission.

In some examples, the UE may identify a status based on a unicastconnection associated with the one or more resources (e.g., for sidelinkcommunications). For example, the UE may determine (e.g., based on areceived coordination message) that one or more resources are preferredfor a first unicast connection. The UE may determine that the one ormore resources are preferred or non-preferred for a second unicastconnection based on the one or more resources being preferred for thefirst unicast connection. In some cases, the coordination message mayindicate or include a destination identifier, a source identifier, aunicast connection associated with the one or more resources, or somecombination thereof.

A method for wireless communications at a first UE is described. Themethod may include receiving, from a second UE, a coordination messageover a sidelink channel that indicates a preference status ofcommunication resources for sidelink communications between two or moreUEs, identifying a status of one or more communication resources for thesidelink communications based on the received coordination message,where the identified status of each communication resource of the one ormore communication resources indicates whether a respectivecommunication resource is available, reserved, preferred, ornon-preferred, or a combination thereof, and selecting a communicationresource for the sidelink communications based on the identified statusof the one or more communication resources.

An apparatus for wireless communications at a first UE is described. Theapparatus may include a processor, memory coupled with the processor,and instructions stored in the memory. The instructions may beexecutable by the processor to cause the apparatus to receive, from asecond UE, a coordination message over a sidelink channel that indicatesa preference status of communication resources for sidelinkcommunications between two or more UEs, identify a status of one or morecommunication resources for the sidelink communications based on thereceived coordination message, where the identified status of eachcommunication resource of the one or more communication resourcesindicates whether a respective communication resource is available,reserved, preferred, or non-preferred, or a combination thereof, andselect a communication resource for the sidelink communications based onthe identified status of the one or more communication resources.

Another apparatus for wireless communications at a first UE isdescribed. The apparatus may include means for receiving, from a secondUE, a coordination message over a sidelink channel that indicates apreference status of communication resources for sidelink communicationsbetween two or more UEs, means for identifying a status of one or morecommunication resources for the sidelink communications based on thereceived coordination message, where the identified status of eachcommunication resource of the one or more communication resourcesindicates whether a respective communication resource is available,reserved, preferred, or non-preferred, or a combination thereof, andmeans for selecting a communication resource for the sidelinkcommunications based on the identified status of the one or morecommunication resources.

A non-transitory computer-readable medium storing code for wirelesscommunications at a first UE is described. The code may includeinstructions executable by a processor to receive, from a second UE, acoordination message over a sidelink channel that indicates a preferencestatus of communication resources for sidelink communications betweentwo or more UEs, identify a status of one or more communicationresources for the sidelink communications based on the receivedcoordination message, where the identified status of each communicationresource of the one or more communication resources indicates whether arespective communication resource is available, reserved, preferred, ornon-preferred, or a combination thereof, and select a communicationresource for the sidelink communications based on the identified statusof the one or more communication resources.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, identifying the status mayinclude operations, features, means, or instructions for identifyingthat the one or more communication resources may be preferred for thesidelink communications between the two or more UEs or the one or morecommunication resources may be non-preferred for the sidelinkcommunications between the two or more UEs, where the preference statusindicates whether the one or more communication resources may bepreferred or non-preferred for the sidelink communications between thetwo or more UEs.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for transmitting a messagerequesting the coordination message for the sidelink communications,where receiving the coordination message may be based on transmittingthe message.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for identifying whether thefirst UE may be an intended recipient of the coordination message, whereidentifying the status of the one or more communication resources may bebased on identifying whether the first UE may be the intended recipientof the coordination message.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for identifying whether thecoordination message indicates preferred resources or non-preferredresources, where identifying the status of the one or more communicationresources may be based on identifying whether the first UE may be theintended recipient of the coordination message and identifying whetherthe coordination message indicates the preferred resources or thenon-preferred resources.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, identifying the status mayinclude operations, features, means, or instructions for identifyingthat the communication resource may be a preferred resource based on thefirst UE being the intended recipient and the coordination messageindicating the preferred resources.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, identifying the status mayinclude operations, features, means, or instructions for identifyingthat the communication resource may be a non-preferred resource based ona third UE being the intended recipient and the coordination messageindicating the preferred resources.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, identifying the status mayinclude operations, features, means, or instructions for identifyingthat the communication resource may be a non-preferred resource based onthe first UE being the intended recipient and the coordination messageindicating the non-preferred resources.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the coordination messageincludes or may be associated with an indication of the intendedrecipient.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for identifying adestination identifier included in or associated with the coordinationmessage, where identifying whether the first UE may be the intendedrecipient of the coordination message may be based on identifying thedestination identifier.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the destination identifiermay be included in sidelink control information (SCI) associated withthe coordination message.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, identifying whether the firstUE may be the intended recipient of the coordination message may bebased on the coordination message being associated with a process toreserve the communication resource for the sidelink communications.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the coordination messageincludes a portion of a radio resource control (RRC) message, a portionof a medium access control control element (MAC-CE), a portion of afirst-stage SCI, or a portion of a second-stage SCI.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the one or more communicationresources for the sidelink communications may be associated with a firstunicast communication connection between the first UE and the second UEand identifying the status further includes identifying that the one ormore communication resources may be preferred resources of the firstunicast communication connection based on receiving the coordinationmessage.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for identifying that asecond communication resource of a second unicast communicationconnection between the first UE and the second UE may be a preferredresource based on receiving the coordination message for the firstunicast communication connection, the second communication resourcecorresponding to one of the one or more communication resources of thefirst unicast communication connection.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for identifying that asecond communication resource of a second unicast communicationconnection between the first UE and the second UE may be a non-preferredresource based on receiving the coordination message for the firstunicast communication connection that indicates that the one or morecommunication resources may be the preferred resources, the secondcommunication resource corresponding to one of the one or morecommunication resources of the first unicast communication connection.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for identifying that asecond communication resource of a second unicast communicationconnection between the first UE and a third UE may be a non-preferredresource based on receiving the coordination message for the firstunicast communication connection that indicates that the one or morecommunication resources may be the preferred resources, the secondcommunication resource corresponding to one of the one or morecommunication resources of the first unicast communication connection.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the coordination messageindicates a source identifier and a destination identifier and themethod, apparatuses, and non-transitory computer-readable medium mayinclude further operations, features, means, or instructions foridentifying the first unicast communication connection based on thesource identifier and the destination identifier.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the coordination messageincludes a first indication of the first unicast communicationconnection and a second indication of a second unicast communicationconnection.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the coordination messageindicates whether a resource conflict for the one or more communicationresources for the sidelink communications may be detected.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, an indication of the resourceconflict includes a negative acknowledgement (NACK) associated with amessage transmitted by a scheduling UE of the sidelink communications.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for identifying that thecommunication resource may be a preferred resource based on the first UEbeing the intended recipient and the coordination message indicating thepreferred resources.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for identifying that thecommunication resource may be a non-preferred resource based on a thirdUE being the intended recipient and the coordination message indicatingthe preferred resources.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 illustrate examples of wireless communications systemsthat support user equipment (UE) coordination for sidelink in accordancewith aspects of the present disclosure.

FIG. 3 illustrates an example of resource mapping that supports UEcoordination for sidelink in accordance with aspects of the presentdisclosure.

FIG. 4 illustrates an example of a wireless communications system thatsupports UE coordination for sidelink in accordance with aspects of thepresent disclosure.

FIG. 5 illustrates an example of a process flow that supports UEcoordination for sidelink in accordance with aspects of the presentdisclosure.

FIGS. 6 and 7 show block diagrams of devices that support UEcoordination for sidelink in accordance with aspects of the presentdisclosure.

FIG. 8 shows a block diagram of a communications manager that supportsUE coordination for sidelink in accordance with aspects of the presentdisclosure.

FIG. 9 shows a diagram of a system including a device that supports UEcoordination for sidelink in accordance with aspects of the presentdisclosure.

FIGS. 10 through 12 show flowcharts illustrating methods that support UEcoordination for sidelink in accordance with aspects of the presentdisclosure.

DETAILED DESCRIPTION

Some wireless communications systems may support sidelinkcommunications, where user equipment (UEs) may communicate with oneanother over a sidelink channel. UEs communicating via sidelink may notbe scheduled by a central entity (e.g., a base station), and as such,may autonomously select resources (e.g., time resources, frequencyresources) to use for transmissions by determining whether each resource(e.g., of a pool of resources) is available or occupied (e.g., reservedby another sidelink UE). For example, a UE may perform a sensingprocedure during a sensing window to sense a pool of resources anddetermine which, if any, are available. The UE may select resources fromthe available resources, for instance, during a resource selectionwindow, and may use the selected resources to perform sidelinktransmissions.

In some examples, a UE may generate and share coordination informationwith one or more other UEs via a coordination message transmitted over asidelink connection, e.g., to assist in resource selection. Coordinationinformation may include information (e.g., a preference status) aboutone or more resources of the pool of resources. For example, a first UEmay transmit, to a second UE (e.g., and one or more additional UEs), acoordination message that includes an indication that one or moreresources are preferred for transmissions of the second UE.Additionally, or alternatively, the coordination message may include anindication that one or more resources are not preferred fortransmissions of the second UE, or may indicate a resource conflict. Thesecond UE may use the coordination information (e.g., in combinationwith a sensing procedure) to select resources (e.g., during a resourceselection window). For instance, the second UE may select resources thatwere indicated as preferred by the coordination message.

In some cases, however, the quantity of other UEs to which the first UEmay transmit coordination messages may be relatively large. If thecoordination messages are UE-specific (e.g., generated for andtransmitted to each receiving UE separately), transmitting acoordination message to every UE may consume a considerable amount oftime and/or network resources. Additionally, UEs communicating viasidelink may operate using half-duplex communications; thus, a UE thatis transmitting over a sidelink channel may be unable to receiveinformation (such as a coordination message) over another sidelinkchannel, e.g., for the duration of the transmission.

To avoid missing such reception opportunities and to increase efficiencyin resource allocation for sidelink communications, a receiving UE mayinterpret coordination information of a received coordination messagebased on whether the receiving UE is an intended recipient of thecoordination message. That is, the coordination message may include anindication of the intended recipient, such as a destination identifier,or an indication of a communication connection associated with theresources, that the receiving UE may use to identify a status of theresources. For example, if the receiving UE is the intended recipient(e.g., as indicated by the destination identifier), the receiving UE mayidentify that the status of the or more indicated resources ispreferred. If the receiving UE is not the intended recipient, thereceiving UE may identify that the status of the one or more indicatedresources is non-preferred, e.g., as the resources are intended to beindicated as preferred for another UE associated with the destinationidentifier.

Additionally, or alternatively, the receiving UE may interpret thecoordination message based on a communication connection associated withthe resources. For example, the receiving UE may have one or moreunicast connections with one or more other UEs. The coordination messagemay include an indication that the coordination information isassociated with a first unicast connection and that one or moreresources are preferred for the first unicast connection. The receivingUE may determine that the one or more resources are preferred for thefirst unicast connection and are non-preferred for a second unicastconnection. In some examples, if the coordination message indicates thatthe first and second unicast connections are with a same UE, thereceiving UE may instead determine that the one or more resources arepreferred for both the first and second unicast connections.

Aspects of the disclosure are initially described in the context ofwireless communications systems. Aspects of the disclosure are thendescribed with reference to a resource selection procedure and a processflow. Aspects of the disclosure are further illustrated by and describedwith reference to apparatus diagrams, system diagrams, and flowchartsthat relate to UE coordination for sidelink.

FIG. 1 illustrates an example of a wireless communications system 100that supports UE coordination for sidelink in accordance with aspects ofthe present disclosure. The wireless communications system 100 mayinclude one or more base stations 105, one or more UEs 115, and a corenetwork 130. In some examples, the wireless communications system 100may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A)network, an LTE-A Pro network, or a New Radio (NR) network. In someexamples, the wireless communications system 100 may support enhancedbroadband communications, ultra-reliable (e.g., mission critical)communications, low latency communications, communications with low-costand low-complexity devices, or any combination thereof.

The base stations 105 may be dispersed throughout a geographic area toform the wireless communications system 100 and may be devices indifferent forms or having different capabilities. The base stations 105and the UEs 115 may wirelessly communicate via one or more communicationlinks 125. Each base station 105 may provide a coverage area 110 overwhich the UEs 115 and the base station 105 may establish one or morecommunication links 125. The coverage area 110 may be an example of ageographic area over which a base station 105 and a UE 115 may supportthe communication of signals according to one or more radio accesstechnologies.

The UEs 115 may be dispersed throughout a coverage area 110 of thewireless communications system 100, and each UE 115 may be stationary,or mobile, or both at different times. The UEs 115 may be devices indifferent forms or having different capabilities. Some example UEs 115are illustrated in FIG. 1 . The UEs 115 described herein may be able tocommunicate with various types of devices, such as other UEs 115, thebase stations 105, or network equipment (e.g., core network nodes, relaydevices, integrated access and backhaul (IAB) nodes, or other networkequipment), as shown in FIG. 1 .

The base stations 105 may communicate with the core network 130, or withone another, or both. For example, the base stations 105 may interfacewith the core network 130 through one or more backhaul links 120 (e.g.,via an S1, N2, N3, or other interface). The base stations 105 maycommunicate with one another over the backhaul links 120 (e.g., via anX2, Xn, or other interface) either directly (e.g., directly between basestations 105), or indirectly (e.g., via core network 130), or both. Insome examples, the backhaul links 120 may be or include one or morewireless links.

One or more of the base stations 105 described herein may include or maybe referred to by a person having ordinary skill in the art as a basetransceiver station, a radio base station, an access point, a radiotransceiver, a NodeB, an eNodeB (eNB), a next-generation NodeB or agiga-NodeB (either of which may be referred to as a gNB), a Home NodeB,a Home eNodeB, or other suitable terminology.

A UE 115 may include or may be referred to as a mobile device, awireless device, a remote device, a handheld device, or a subscriberdevice, or some other suitable terminology, where the “device” may alsobe referred to as a unit, a station, a terminal, or a client, amongother examples. A UE 115 may also include or may be referred to as apersonal electronic device such as a cellular phone, a personal digitalassistant (PDA), a tablet computer, a laptop computer, or a personalcomputer. In some examples, a UE 115 may include or be referred to as awireless local loop (WLL) station, an Internet of Things (IoT) device,an Internet of Everything (IoE) device, or a machine type communications(MTC) device, among other examples, which may be implemented in variousobjects such as appliances, or vehicles, meters, among other examples.

The UEs 115 described herein may be able to communicate with varioustypes of devices, such as other UEs 115 that may sometimes act as relaysas well as the base stations 105 and the network equipment includingmacro eNBs or gNBs, small cell eNBs or gNBs, or relay base stations,among other examples, as shown in FIG. 1 .

The UEs 115 and the base stations 105 may wirelessly communicate withone another via one or more communication links 125 over one or morecarriers. The term “carrier” may refer to a set of radio frequencyspectrum resources having a defined physical layer structure forsupporting the communication links 125. For example, a carrier used fora communication link 125 may include a portion of a radio frequencyspectrum band (e.g., a bandwidth part (BWP)) that is operated accordingto one or more physical layer channels for a given radio accesstechnology (e.g., LTE, LTE-A, LTE-A Pro, NR). Each physical layerchannel may carry acquisition signaling (e.g., synchronization signals,system information), control signaling that coordinates operation forthe carrier, user data, or other signaling. The wireless communicationssystem 100 may support communication with a UE 115 using carrieraggregation or multi-carrier operation. A UE 115 may be configured withmultiple downlink component carriers and one or more uplink componentcarriers according to a carrier aggregation configuration. Carrieraggregation may be used with both frequency division duplexing (FDD) andtime division duplexing (TDD) component carriers.

In some examples (e.g., in a carrier aggregation configuration), acarrier may also have acquisition signaling or control signaling thatcoordinates operations for other carriers. A carrier may be associatedwith a frequency channel (e.g., an evolved universal mobiletelecommunication system terrestrial radio access (E-UTRA) absoluteradio frequency channel number (EARFCN)) and may be positioned accordingto a channel raster for discovery by the UEs 115. A carrier may beoperated in a standalone mode where initial acquisition and connectionmay be conducted by the UEs 115 via the carrier, or the carrier may beoperated in a non-standalone mode where a connection is anchored using adifferent carrier (e.g., of the same or a different radio accesstechnology).

The communication links 125 shown in the wireless communications system100 may include uplink transmissions from a UE 115 to a base station105, or downlink transmissions from a base station 105 to a UE 115.Carriers may carry downlink or uplink communications (e.g., in an FDDmode) or may be configured to carry downlink and uplink communications(e.g., in a TDD mode).

A carrier may be associated with a particular bandwidth of the radiofrequency spectrum, and in some examples the carrier bandwidth may bereferred to as a “system bandwidth” of the carrier or the wirelesscommunications system 100. For example, the carrier bandwidth may be oneof a number of determined bandwidths for carriers of a particular radioaccess technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 megahertz(MHz)). Devices of the wireless communications system 100 (e.g., thebase stations 105, the UEs 115, or both) may have hardwareconfigurations that support communications over a particular carrierbandwidth or may be configurable to support communications over one of aset of carrier bandwidths. In some examples, the wireless communicationssystem 100 may include base stations 105 or UEs 115 that supportsimultaneous communications via carriers associated with multiplecarrier bandwidths. In some examples, each served UE 115 may beconfigured for operating over portions (e.g., a sub-band, a BWP) or allof a carrier bandwidth.

Signal waveforms transmitted over a carrier may be made up of multiplesubcarriers (e.g., using multi-carrier modulation (MCM) techniques suchas orthogonal frequency division multiplexing (OFDM) or discrete Fouriertransform spread OFDM (DFT-S-OFDM)). In a system employing MCMtechniques, a resource element may consist of one symbol period (e.g., aduration of one modulation symbol) and one subcarrier, where the symbolperiod and subcarrier spacing are inversely related. The number of bitscarried by each resource element may depend on the modulation scheme(e.g., the order of the modulation scheme, the coding rate of themodulation scheme, or both). Thus, the more resource elements that a UE115 receives and the higher the order of the modulation scheme, thehigher the data rate may be for the UE 115. A wireless communicationsresource may refer to a combination of a radio frequency spectrumresource, a time resource, and a spatial resource (e.g., spatial layersor beams), and the use of multiple spatial layers may further increasethe data rate or data integrity for communications with a UE 115.

The time intervals for the base stations 105 or the UEs 115 may beexpressed in multiples of a basic time unit which may, for example,refer to a sampling period of T_(s)=1/(Δf_(max)·N_(f)) seconds, whereΔf_(max) may represent the maximum supported subcarrier spacing, andN_(f) may represent the maximum supported discrete Fourier transform(DFT) size. Time intervals of a communications resource may be organizedaccording to radio frames each having a specified duration (e.g., 10milliseconds (ms)). Each radio frame may be identified by a system framenumber (SFN) (e.g., ranging from 0 to 1023).

Each frame may include multiple consecutively numbered subframes orslots, and each subframe or slot may have the same duration. In someexamples, a frame may be divided (e.g., in the time domain) intosubframes, and each subframe may be further divided into a number ofslots. Alternatively, each frame may include a variable number of slots,and the number of slots may depend on subcarrier spacing. Each slot mayinclude a number of symbol periods (e.g., depending on the length of thecyclic prefix prepended to each symbol period). In some wirelesscommunications systems 100, a slot may further be divided into multiplemini-slots containing one or more symbols. Excluding the cyclic prefix,each symbol period may contain one or more (e.g., N_(f)) samplingperiods. The duration of a symbol period may depend on the subcarrierspacing or frequency band of operation.

A subframe, a slot, a mini-slot, or a symbol may be the smallestscheduling unit (e.g., in the time domain) of the wirelesscommunications system 100 and may be referred to as a transmission timeinterval (TTI). In some examples, the TTI duration (e.g., the number ofsymbol periods in a TTI) may be variable. Additionally or alternatively,the smallest scheduling unit of the wireless communications system 100may be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs)).

Physical channels may be multiplexed on a carrier according to varioustechniques. A physical control channel and a physical data channel maybe multiplexed on a downlink carrier, for example, using one or more oftime division multiplexing (TDM) techniques, frequency divisionmultiplexing (FDM) techniques, or hybrid TDM-FDM techniques. A controlregion (e.g., a control resource set (CORESET)) for a physical controlchannel may be defined by a number of symbol periods and may extendacross the system bandwidth or a subset of the system bandwidth of thecarrier. One or more control regions (e.g., CORESETs) may be configuredfor a set of the UEs 115. For example, one or more of the UEs 115 maymonitor or search control regions for control information according toone or more search space sets, and each search space set may include oneor multiple control channel candidates in one or more aggregation levelsarranged in a cascaded manner. An aggregation level for a controlchannel candidate may refer to a number of control channel resources(e.g., control channel elements (CCEs)) associated with encodedinformation for a control information format having a given payloadsize. Search space sets may include common search space sets configuredfor sending control information to multiple UEs 115 and UE-specificsearch space sets for sending control information to a specific UE 115.

Each base station 105 may provide communication coverage via one or morecells, for example a macro cell, a small cell, a hot spot, or othertypes of cells, or any combination thereof. The term “cell” may refer toa logical communication entity used for communication with a basestation 105 (e.g., over a carrier) and may be associated with anidentifier for distinguishing neighboring cells (e.g., a physical cellidentifier (PCID), a virtual cell identifier (VCID), or others). In someexamples, a cell may also refer to a geographic coverage area 110 or aportion of a geographic coverage area 110 (e.g., a sector) over whichthe logical communication entity operates. Such cells may range fromsmaller areas (e.g., a structure, a subset of structure) to larger areasdepending on various factors such as the capabilities of the basestation 105. For example, a cell may be or include a building, a subsetof a building, or exterior spaces between or overlapping with geographiccoverage areas 110, among other examples.

A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by theUEs 115 with service subscriptions with the network provider supportingthe macro cell. A small cell may be associated with a lower-powered basestation 105, as compared with a macro cell, and a small cell may operatein the same or different (e.g., licensed, unlicensed) frequency bands asmacro cells. Small cells may provide unrestricted access to the UEs 115with service subscriptions with the network provider or may providerestricted access to the UEs 115 having an association with the smallcell (e.g., the UEs 115 in a closed subscriber group (CSG), the UEs 115associated with users in a home or office). A base station 105 maysupport one or multiple cells and may also support communications overthe one or more cells using one or multiple component carriers.

In some examples, a carrier may support multiple cells, and differentcells may be configured according to different protocol types (e.g.,MTC, narrowband IoT (NB-IoT), enhanced mobile broadband (eMBB)) that mayprovide access for different types of devices.

In some examples, a base station 105 may be movable and thereforeprovide communication coverage for a moving geographic coverage area110. In some examples, different geographic coverage areas 110associated with different technologies may overlap, but the differentgeographic coverage areas 110 may be supported by the same base station105. In other examples, the overlapping geographic coverage areas 110associated with different technologies may be supported by differentbase stations 105. The wireless communications system 100 may include,for example, a heterogeneous network in which different types of thebase stations 105 provide coverage for various geographic coverage areas110 using the same or different radio access technologies.

The wireless communications system 100 may support synchronous orasynchronous operation. For synchronous operation, the base stations 105may have similar frame timings, and transmissions from different basestations 105 may be approximately aligned in time. For asynchronousoperation, the base stations 105 may have different frame timings, andtransmissions from different base stations 105 may, in some examples,not be aligned in time. The techniques described herein may be used foreither synchronous or asynchronous operations.

Some UEs 115, such as MTC or IoT devices, may be low cost or lowcomplexity devices and may provide for automated communication betweenmachines (e.g., via Machine-to-Machine (M2M) communication). M2Mcommunication or MTC may refer to data communication technologies thatallow devices to communicate with one another or a base station 105without human intervention. In some examples, M2M communication or MTCmay include communications from devices that integrate sensors or metersto measure or capture information and relay such information to acentral server or application program that makes use of the informationor presents the information to humans interacting with the applicationprogram. Some UEs 115 may be designed to collect information or enableautomated behavior of machines or other devices. Examples ofapplications for MTC devices include smart metering, inventorymonitoring, water level monitoring, equipment monitoring, healthcaremonitoring, wildlife monitoring, weather and geological eventmonitoring, fleet management and tracking, remote security sensing,physical access control, and transaction-based business charging.

Some UEs 115 may be configured to employ operating modes that reducepower consumption, such as half-duplex communications (e.g., a mode thatsupports one-way communication via transmission or reception, but nottransmission and reception simultaneously). In some examples,half-duplex communications may be performed at a reduced peak rate.Other power conservation techniques for the UEs 115 include entering apower saving deep sleep mode when not engaging in active communications,operating over a limited bandwidth (e.g., according to narrowbandcommunications), or a combination of these techniques. For example, someUEs 115 may be configured for operation using a narrowband protocol typethat is associated with a defined portion or range (e.g., set ofsubcarriers or resource blocks (RBs)) within a carrier, within aguard-band of a carrier, or outside of a carrier.

The wireless communications system 100 may be configured to supportultra-reliable communications or low-latency communications, or variouscombinations thereof. For example, the wireless communications system100 may be configured to support ultra-reliable low-latencycommunications (URLLC) or mission critical communications. The UEs 115may be designed to support ultra-reliable, low-latency, or criticalfunctions (e.g., mission critical functions). Ultra-reliablecommunications may include private communication or group communicationand may be supported by one or more mission critical services such asmission critical push-to-talk (MCPTT), mission critical video (MCVideo),or mission critical data (MCData). Support for mission criticalfunctions may include prioritization of services, and mission criticalservices may be used for public safety or general commercialapplications. The terms ultra-reliable, low-latency, mission critical,and ultra-reliable low-latency may be used interchangeably herein.

In some examples, a UE 115 may also be able to communicate directly withother UEs 115 over a device-to-device (D2D) communication link 135(e.g., using a peer-to-peer (P2P) or D2D protocol). One or more UEs 115utilizing D2D communications may be within the geographic coverage area110 of a base station 105. Other UEs 115 in such a group may be outsidethe geographic coverage area 110 of a base station 105 or be otherwiseunable to receive transmissions from a base station 105. In someexamples, groups of the UEs 115 communicating via D2D communications mayutilize a one-to-many (1:M) system in which each UE 115 transmits toevery other UE 115 in the group. In some examples, a base station 105facilitates the scheduling of resources for D2D communications. In othercases, D2D communications are carried out between the UEs 115 withoutthe involvement of a base station 105.

In some systems, the D2D communication link 135 may be an example of acommunication channel, such as a sidelink communication channel, betweenvehicles (e.g., UEs 115). In some examples, vehicles may communicateusing vehicle-to-everything (V2X) communications, vehicle-to-vehicle(V2V) communications, or some combination of these. A vehicle may signalinformation related to traffic conditions, signal scheduling, weather,safety, emergencies, or any other information relevant to a V2X system.In some examples, vehicles in a V2X system may communicate with roadsideinfrastructure, such as roadside units, or with the network via one ormore network nodes (e.g., base stations 105) using vehicle-to-network(V2N) communications, or with both.

The core network 130 may provide user authentication, accessauthorization, tracking, Internet Protocol (IP) connectivity, and otheraccess, routing, or mobility functions. The core network 130 may be anevolved packet core (EPC) or 5G core (5GC), which may include at leastone control plane entity that manages access and mobility (e.g., amobility management entity (MME), an access and mobility managementfunction (AMF)) and at least one user plane entity that routes packetsor interconnects to external networks (e.g., a serving gateway (S-GW), aPacket Data Network (PDN) gateway (P-GW), or a user plane function(UPF)). The control plane entity may manage non-access stratum (NAS)functions such as mobility, authentication, and bearer management forthe UEs 115 served by the base stations 105 associated with the corenetwork 130. User IP packets may be transferred through the user planeentity, which may provide IP address allocation as well as otherfunctions. The user plane entity may be connected to IP services 150 forone or more network operators. The IP services 150 may include access tothe Internet, Intranet(s), an IP Multimedia Subsystem (IMS), or aPacket-Switched Streaming Service.

Some of the network devices, such as a base station 105, may includesubcomponents such as an access network entity 140, which may be anexample of an access node controller (ANC). Each access network entity140 may communicate with the UEs 115 through one or more other accessnetwork transmission entities 145, which may be referred to as radioheads, smart radio heads, or transmission/reception points (TRPs). Eachaccess network transmission entity 145 may include one or more antennapanels. In some configurations, various functions of each access networkentity 140 or base station 105 may be distributed across various networkdevices (e.g., radio heads and ANCs) or consolidated into a singlenetwork device (e.g., a base station 105).

The wireless communications system 100 may operate using one or morefrequency bands, typically in the range of 300 megahertz (MHz) to 300gigahertz (GHz). Generally, the region from 300 MHz to 3 GHz is known asthe ultra-high frequency (UHF) region or decimeter band because thewavelengths range from approximately one decimeter to one meter inlength. The UHF waves may be blocked or redirected by buildings andenvironmental features, but the waves may penetrate structuressufficiently for a macro cell to provide service to the UEs 115 locatedindoors. The transmission of UHF waves may be associated with smallerantennas and shorter ranges (e.g., less than 100 kilometers) compared totransmission using the smaller frequencies and longer waves of the highfrequency (HF) or very high frequency (VHF) portion of the spectrumbelow 300 MHz.

The wireless communications system 100 may also operate in a super highfrequency (SHF) region using frequency bands from 3 GHz to 30 GHz, alsoknown as the centimeter band, or in an extremely high frequency (EHF)region of the spectrum (e.g., from 30 GHz to 300 GHz), also known as themillimeter band. In some examples, the wireless communications system100 may support millimeter wave (mmW) communications between the UEs 115and the base stations 105, and EHF antennas of the respective devicesmay be smaller and more closely spaced than UHF antennas. In someexamples, this may facilitate use of antenna arrays within a device. Thepropagation of EHF transmissions, however, may be subject to evengreater atmospheric attenuation and shorter range than SHF or UHFtransmissions. The techniques disclosed herein may be employed acrosstransmissions that use one or more different frequency regions, anddesignated use of bands across these frequency regions may differ bycountry or regulating body.

The wireless communications system 100 may utilize both licensed andunlicensed radio frequency spectrum bands. For example, the wirelesscommunications system 100 may employ License Assisted Access (LAA),LTE-Unlicensed (LTE-U) radio access technology, or NR technology in anunlicensed band such as the 5 GHz industrial, scientific, and medical(ISM) band. When operating in unlicensed radio frequency spectrum bands,devices such as the base stations 105 and the UEs 115 may employ carriersensing for collision detection and avoidance. In some examples,operations in unlicensed bands may be based on a carrier aggregationconfiguration in conjunction with component carriers operating in alicensed band (e.g., LAA). Operations in unlicensed spectrum may includedownlink transmissions, uplink transmissions, P2P transmissions, or D2Dtransmissions, among other examples.

A base station 105 or a UE 115 may be equipped with multiple antennas,which may be used to employ techniques such as transmit diversity,receive diversity, multiple-input multiple-output (MIMO) communications,or beamforming. The antennas of a base station 105 or a UE 115 may belocated within one or more antenna arrays or antenna panels, which maysupport MIMO operations or transmit or receive beamforming. For example,one or more base station antennas or antenna arrays may be co-located atan antenna assembly, such as an antenna tower. In some examples,antennas or antenna arrays associated with a base station 105 may belocated in diverse geographic locations. A base station 105 may have anantenna array with a number of rows and columns of antenna ports thatthe base station 105 may use to support beamforming of communicationswith a UE 115. Likewise, a UE 115 may have one or more antenna arraysthat may support various MIMO or beamforming operations. Additionally oralternatively, an antenna panel may support radio frequency beamformingfor a signal transmitted via an antenna port.

The base stations 105 or the UEs 115 may use MIMO communications toexploit multipath signal propagation and increase the spectralefficiency by transmitting or receiving multiple signals via differentspatial layers. Such techniques may be referred to as spatialmultiplexing. The multiple signals may, for example, be transmitted bythe transmitting device via different antennas or different combinationsof antennas. Likewise, the multiple signals may be received by thereceiving device via different antennas or different combinations ofantennas. Each of the multiple signals may be referred to as a separatespatial stream and may carry bits associated with the same data stream(e.g., the same codeword) or different data streams (e.g., differentcodewords). Different spatial layers may be associated with differentantenna ports used for channel measurement and reporting. MIMOtechniques include single-user MIMO (SU-MIMO), where multiple spatiallayers are transmitted to the same receiving device, and multiple-userMIMO (MU-MIMO), where multiple spatial layers are transmitted tomultiple devices.

Beamforming, which may also be referred to as spatial filtering,directional transmission, or directional reception, is a signalprocessing technique that may be used at a transmitting device or areceiving device (e.g., a base station 105, a UE 115) to shape or steeran antenna beam (e.g., a transmit beam, a receive beam) along a spatialpath between the transmitting device and the receiving device.Beamforming may be achieved by combining the signals communicated viaantenna elements of an antenna array such that some signals propagatingat particular orientations with respect to an antenna array experienceconstructive interference while others experience destructiveinterference. The adjustment of signals communicated via the antennaelements may include a transmitting device or a receiving deviceapplying amplitude offsets, phase offsets, or both to signals carriedvia the antenna elements associated with the device. The adjustmentsassociated with each of the antenna elements may be defined by abeamforming weight set associated with a particular orientation (e.g.,with respect to the antenna array of the transmitting device orreceiving device, or with respect to some other orientation).

A base station 105 or a UE 115 may use beam sweeping techniques as partof beam forming operations. For example, a base station 105 may usemultiple antennas or antenna arrays (e.g., antenna panels) to conductbeamforming operations for directional communications with a UE 115.Some signals (e.g., synchronization signals, reference signals, beamselection signals, or other control signals) may be transmitted by abase station 105 multiple times in different directions. For example,the base station 105 may transmit a signal according to differentbeamforming weight sets associated with different directions oftransmission. Transmissions in different beam directions may be used toidentify (e.g., by a transmitting device, such as a base station 105, orby a receiving device, such as a UE 115) a beam direction for latertransmission or reception by the base station 105.

Some signals, such as data signals associated with a particularreceiving device, may be transmitted by a base station 105 in a singlebeam direction (e.g., a direction associated with the receiving device,such as a UE 115). In some examples, the beam direction associated withtransmissions along a single beam direction may be determined based on asignal that was transmitted in one or more beam directions. For example,a UE 115 may receive one or more of the signals transmitted by the basestation 105 in different directions and may report to the base station105 an indication of the signal that the UE 115 received with a highestsignal quality or an otherwise acceptable signal quality.

In some examples, transmissions by a device (e.g., by a base station 105or a UE 115) may be performed using multiple beam directions, and thedevice may use a combination of digital precoding or radio frequencybeamforming to generate a combined beam for transmission (e.g., from abase station 105 to a UE 115). The UE 115 may report feedback thatindicates precoding weights for one or more beam directions, and thefeedback may correspond to a configured number of beams across a systembandwidth or one or more sub-bands. The base station 105 may transmit areference signal (e.g., a cell-specific reference signal (CRS), achannel state information reference signal (CSI-RS)), which may beprecoded or unprecoded. The UE 115 may provide feedback for beamselection, which may be a precoding matrix indicator (PMI) orcodebook-based feedback (e.g., a multi-panel type codebook, a linearcombination type codebook, a port selection type codebook). Althoughthese techniques are described with reference to signals transmitted inone or more directions by a base station 105, a UE 115 may employsimilar techniques for transmitting signals multiple times in differentdirections (e.g., for identifying a beam direction for subsequenttransmission or reception by the UE 115) or for transmitting a signal ina single direction (e.g., for transmitting data to a receiving device).

A receiving device (e.g., a UE 115) may try multiple receiveconfigurations (e.g., directional listening) when receiving varioussignals from the base station 105, such as synchronization signals,reference signals, beam selection signals, or other control signals. Forexample, a receiving device may try multiple receive directions byreceiving via different antenna subarrays, by processing receivedsignals according to different antenna subarrays, by receiving accordingto different receive beamforming weight sets (e.g., differentdirectional listening weight sets) applied to signals received atmultiple antenna elements of an antenna array, or by processing receivedsignals according to different receive beamforming weight sets appliedto signals received at multiple antenna elements of an antenna array,any of which may be referred to as “listening” according to differentreceive configurations or receive directions. In some examples, areceiving device may use a single receive configuration to receive alonga single beam direction (e.g., when receiving a data signal). The singlereceive configuration may be aligned in a beam direction determinedbased on listening according to different receive configurationdirections (e.g., a beam direction determined to have a highest signalstrength, highest signal-to-noise ratio (SNR), or otherwise acceptablesignal quality based on listening according to multiple beamdirections).

The wireless communications system 100 may be a packet-based networkthat operates according to a layered protocol stack. In the user plane,communications at the bearer or Packet Data Convergence Protocol (PDCP)layer may be IP-based. A Radio Link Control (RLC) layer may performpacket segmentation and reassembly to communicate over logical channels.A Medium Access Control (MAC) layer may perform priority handling andmultiplexing of logical channels into transport channels. The MAC layermay also use error detection techniques, error correction techniques, orboth to support retransmissions at the MAC layer to improve linkefficiency. In the control plane, the Radio Resource Control (RRC)protocol layer may provide establishment, configuration, and maintenanceof an RRC connection between a UE 115 and a base station 105 or a corenetwork 130 supporting radio bearers for user plane data. At thephysical layer, transport channels may be mapped to physical channels.

The UEs 115 and the base stations 105 may support retransmissions ofdata to increase the likelihood that data is received successfully.Hybrid automatic repeat request (HARQ) feedback is one technique forincreasing the likelihood that data is received correctly over acommunication link 125. HARQ may include a combination of errordetection (e.g., using a cyclic redundancy check (CRC)), forward errorcorrection (FEC), and retransmission (e.g., automatic repeat request(ARQ)). HARQ may improve throughput at the MAC layer in poor radioconditions (e.g., low signal-to-noise conditions). In some examples, adevice may support same-slot HARQ feedback, where the device may provideHARQ feedback in a specific slot for data received in a previous symbolin the slot. In other cases, the device may provide HARQ feedback in asubsequent slot, or according to some other time interval.

In some cases, two UEs 115 may communicate with each other via acommunication link 135 (e.g., a sidelink connection or a sidelinkcommunication link). In such cases, for example, a first UE 115 mayreceive one or more sidelink transmissions from a second UE 115 over asidelink channel, which may include one or both of a sidelink controlchannel or a sidelink data channel. For example, the first UE 115 mayreceive a first stage of SCI (which may be referred to herein as SCI-1)over a sidelink control channel, such as a physical sidelink controlchannel (PSCCH), and a second stage of SCI (which may be referred toherein as SCI-2) and data over a sidelink data channel, such as aphysical sidelink shared channel (PSSCH).

To receive a sidelink transmission (e.g., an SCI-1, an SCI-2, etc.), thefirst UE 115 may perform blind decoding over sidelink subchannels. Thefirst UE 115 may receive and decode an SCI-1 in the PSCCH, where theSCI-1 includes PSSCH bandwidth information and resource reservations forfuture slots. After decoding the PSCCH, the first UE 115 may receive anSCI-2. The SCI-2 may include a source identifier indicating thetransmitting device (e.g., the second UE 115, a base station 105) and/ora destination identifier indicating the intended receiving device (e.g.,the first UE 115, the second UE 115, a different UE 115, etc.). Thefirst UE 115 may use the destination identifier to determine whether theSCI-2 is for the first UE 115.

In some scenarios, the first UE 115 and the second UE 115 may determineor otherwise identify a resource allocation for communications betweenthe first UE 115 and the second UE 115 (which may be carried over a PC5link) according to various modes. In a first mode (e.g., mode 1), forexample, a serving base station 105 may assign the transmissionresources for sidelink communications between the first UE 115 and thesecond UE 115 through downlink control information (DCI), such as DCI3_0.

In a second mode, the second UE 115 (e.g., the transmitting UE 115), mayautonomously (e.g., without signaling from the base station 105) selectresources for sidelink communications between the first UE 115 and thesecond UE 115. Further, in the second mode, the second UE 115 mayperform channel sensing based on blind decoding PSCCH channels (e.g.,all PSCCH channels) to determine or otherwise identify which resourcesof the PSCCH are reserved by other UEs 115 for other sidelinktransmissions. That is, the second UE 115 may determine or otherwiseidentify which resources of a resource pool are available to use fortransmissions to the first UE 115 (e.g., or other UEs 115 via sidelinkchannels). The second UE 115 may select one or more resources from theavailable resources of the resource pool, for example, during a resourceselection window, and may transmit a message using the selected one ormore resources.

According to the techniques described herein, the first UE 115 and thesecond UE 115 may utilize coordination information of a coordinationmessage to more efficiently and reliably select resources for sidelinkcommunications. For instance, the first UE 115 may transmit, to thesecond UE 115, a coordination message. In some examples, the second UE115 may transmit, to the first UE 115, a message including a request forthe coordination message. The coordination message may be included aspart of an RRC message, a MAC-CE, SCI-1, or SCI-2. The coordinationmessage may include coordination information that indicates a preferencestatus of resources for sidelink communications between two or more UEs115 (which may or may not include the first UE 115 and/or the second UE115), such as whether a given resource is preferred or non-preferred.The second UE 115 may identify a status of one or more resources basedon the coordination information (e.g., the preference statusinformation) included in the coordination message, and, in some cases,based on channel sensing. For instance, the second UE 115 may identifythat a respective resource is available, reserved, preferred,non-preferred, or a combination thereof. The second UE 115 may selectresources for sidelink communications based on the identified status.

As an example, the coordination message may indicate that a firstresource is preferred for the second UE 115. The second UE 115 maydetermine that the first resource has a status of preferred and a statusof available, for instance, based on the indication in the coordinationmessage and a channel sensing procedure performed by the second UE 115.The coordination message may indicate that a second resource isnon-preferred for the second UE 115. During a resource selection window,the second UE 115 may select at least the first resource and may refrainfrom selecting at least the second resource. The second UE 115 maytransmit a sidelink message using at least the first resource.

In some examples, the second UE 115 may determine or otherwise identifya status of one or more of the resources based on the intended recipientof the coordination message, which may, in some cases, be indicated bythe coordination message or by SCI-2 associated with the coordinationmessage. For example, the coordination message may include an indicationof the intended recipient, such as a destination identifier; as anotherexample, the coordination message may be associated with or may includean SCI-2, and the SCI-2 may include the indication of the intendedrecipient (e.g., as a destination identifier). If the second UE 115determines that the second UE 115 is the intended recipient of thecoordination message, the second UE 115 may identify that the one ormore resources indicated in the coordination message are preferred forthe second UE 115. Alternatively, if the second UE 115 is not theintended recipient, the second UE 115 may identify that the one or moreresources indicated in the coordination message are preferred for adifferent UE 115 (i.e., the intended recipient) and thus arenon-preferred for the second UE 115.

The second UE 115 may additionally or alternatively identify whether thesecond UE 115 is an intended recipient based on an implicit associationbetween the coordination message and one or more of the resources. Forinstance, the second UE 115 may transmit a request for the coordinationmessage on a first resource and may receive the coordination message ona second resource; the second UE 115 may identify that the coordinationmessage is intended for the second UE 115 based on the coordinationmessage being received on the second resource. As another example, thesecond UE 115 may determine that the second UE 115 is an intendedrecipient by identifying that the coordination message is associatedwith a process to reserve the one or more resources. Additionally, oralternatively, the coordination message may be received on a resourcethat is associated with a resource indicated in the coordinationmessage; the second UE 115 may identify the resource indicated in thecoordination message based on identifying the association.

In some cases, the second UE 115 may have multiple unicast connectionswith other UEs 115 including the first UE 115. The second UE 115 mayidentify a status of the one or more resources for each unicastconnection based on the coordination message. For example, if acoordination message indicates that the one or more resources arepreferred for a first unicast connection with the first UE 115, thesecond UE 115 may determine that the one or more resources arenon-preferred for a second unicast connection with a third UE 115. Insome examples, the coordination message may include or may be associatedwith an indication (e.g., a source identifier and a destinationidentifier) that both the first and second unicast connections are witha same UE 115, such as the first UE 115. In such examples, the second UE115 may determine that the one or more resources indicated as preferredfor the first unicast connection are also preferred for the secondunicast connection. Alternatively, the second UE 115 may determine thatthe one or more resources indicated as preferred for the first unicastconnection are non-preferred for the second unicast connection.

FIG. 2 illustrates an example of a wireless communications system 200that supports UE coordination for sidelink in accordance with aspects ofthe present disclosure. The wireless communications system 200 mayimplement aspects of the wireless communications system 100. Forexample, the wireless communications system 200 may include a coveragearea 110-a and UEs 115 and a base station 105, which may be examples ofthe corresponding devices described herein. The UE 115-a may communicatewith the base station 105-a via a communication link 205. The UEs 115may communicate with one another via sidelinks 210 (e.g., sidelinkcommunication links, which may also be referred to as sidelinkconnections). For instance, the UEs 115 may transmit and receivesidelink messages 215.

The UEs 115 in FIG. 2 may operate in a first mode (e.g., mode 1) or asecond mode (e.g., mode 2) for sidelink communications. In the firstmode, for example, the UE 115-a may receive an indication of a resourceallocation from the base station 105-a via communication link 205. Here,the base station 105-a may assign transmission resources for sidelinkcommunications between the UE 115-a and the UEs 115-b and 115-c throughDCI. For example, the base station 105-a may transmit, to the UE 115-a,a DCI indicating an allocation of time and frequency resources and atransmission timing. The UE 115-a may transmit a sidelink transmission215-a to the UE 115-b via the sidelink 210-a using the allocatedresources.

In the example of FIG. 2 , the UEs 115-a, 115-b, and 115-c may operatein the second mode. Thus, the UEs 115-a, 115-b, and 115-c may notreceive sidelink resource allocation information from the base station105-a and may autonomously select resources from a resource pool forcommunicating with one another via sidelinks 210. For example, the UE115-a may perform channel sensing based on blind decoding PSCCH channels(e.g., all PSCCH channels) to determine or otherwise identify whichresources of the resource pool are reserved by other sidelinktransmissions. The pool of resources may include a number of subchannelsover a number of slots and may be shared among the UEs 115, and the UE115-a may perform a sensing procedure, during a sensing window, over thepool of resources to determine occupied (e.g., unavailable) or candidate(e.g., available) resources to use for sidelink transmissions. Forexample, some resources may be reserved for use by the other UEs 115, orsome subchannels may experience relatively high levels of interferencesuch that, even if the UE 115-a transmits a message over thosesubchannels, a receiving UE 115 would have a relatively low likelihoodof successfully receiving and decoding the message.

During a sensing window, a UE 115 (e.g., the UE 115-a, in addition tothe UEs 115-b and 115-c) may perform channel sensing (e.g., sidelinkchannel sensing) by decoding SCI to identify the occupied or availablesidelink resources. In the example of FIG. 2 , each SCI received by a UE115 may be broadcast by a respective UE 115 (e.g., UE 115-a maybroadcast an SCI, UE 115-b may broadcast an SCI, UE 115-c may broadcastan SCI, and so forth) and may indicate sidelink resources reserved bythe respective UE 115. The sensing may be performed, for example, bydecoding scheduling information included in the SCI(s). The UE 115 mayreceive the SCI during a sensing window and may use the informationincluded in the SCI to identify or otherwise determine availableresources, e.g., resources that are not indicated as being reserved inthe SCI(s).

Additionally, a UE 115 (e.g., the UE 115-a, in addition to the UEs 115-band 115-c) may receive, from another UE 115, a coordination message 220that includes coordination information for one or more resources of thepool of resources. In some examples, the coordination message 220 may betransmitted as part of SCI, e.g., as part of SCI-1 or SCI-2, while inother examples, the coordination message 220 may be transmitted as partof an RRC message or a MAC-CE. The coordination message 220 may indicate(e.g., as part of coordination information) a preference status for eachresource of the one or more resources, where the preference statusindicates that a respective resource is preferred or non-preferred(e.g., for sidelink communications between two or more UEs 115). The UE115 may identify a status of the one or more resources based on thepreference status and, in some examples, the results of the sensingprocedure. For instance, the UE 115 may identify that a first resourcehas a status of preferred based on the received coordination message 220and a status of available based on the sensing procedure. The UE 115 maylikewise identify that a second resource has a status of non-preferredbased on the received coordination message 220 and a status of reservedbased on the sensing procedure.

In some examples, the coordination message 220 may include a bitmap toindicate the preference statuses for the one or more resources, whereeach bit corresponds to a resource and the value of the bit indicatesthe preference status (e.g., a value of 1 may correspond to a preferencestatus of preferred while a value of 0 corresponds to a preferencestatus of non-preferred, or vice-versa, among other examples). In otherexamples, the preference status may be indicated via one or more lists,such as a list of time and frequency locations of preferred resourcesand a list of time and frequency locations of non-preferred resources.

Additionally, in some cases, the coordination message 220 may indicatethat a resource may be associated with conflicting transmissions (e.g.,the same resource may be reserved by two different UEs 115) or with aconflict that has already occurred. For example, the coordinationmessage 220 may indicate (e.g., using one or more bits) that a resourceconflict is detected for one or more resources, where the resourceconflict may be between two or more UEs 115. The indication may includea NACK associated with a message transmitted by a scheduling UE, such asthe UE 115-a. In some cases, a UE 115 receiving the coordination message220 may change a resource reservation based on the indicated conflict.

A resource conflict may occur if, for example, two (or more) UEs 115reserve a same resource. UEs 115 communicating via sidelink may operatein a half-duplex mode, where a UE 115 may only communicate in onedirection at a given time. For example, in a time slot, a UE 115 maytransmit a message or receive a message, but may not transmit andreceive simultaneously. Accordingly, if a UE 115, such as the UE 115-a,reserves a resource (e.g., transmits an indication of a resourcereservation, for instance, as part of SCI) at the same time that anotherUE 115, such as the UE 115-b, reserves the same resource, the UE 115-amay not be able to receive the resource reservation from the UE 115-band may be unaware that the UE 115-b has also reserved the resource.Likewise, the UE 115-b may not receive the resource reservation from theUE 115-a and may be unaware of the conflict. Including a conflictindication in a coordination message 220 may enable the UE 115-a and/orthe UE 115-b to resolve the resource conflict, for example, by removingor changing one or both reservations, selecting a different resource,or, if the conflict has already occurred, retransmitting a messageassociated with the conflicting resource.

In addition to a preference status or a conflict indication, thecoordination message 220 may include or may be associated with anindication of an intended recipient of the coordination message 220. Forexample, the coordination message 220 may be associated with (e.g.,transmitted as part of) SCI-2 and the SCI-2 may include a destinationidentifier. Additionally, or alternatively, the coordination message 220may include an explicit indication of an intended recipient of thecoordination message 220. In some examples, the coordination message 220may include explicit indications of the intended recipient for eachrespective portion of the coordination message 220; as an example, thecoordination message 220 may indicate that a first portion is intendedfor the UE 115-a and a second portion is intended for the UE 115-b, orthat a first portion of preference statuses (e.g., corresponding to afirst set of resources) are intended for the UE 115-a and a secondportion of preference statuses (e.g., corresponding to a second set ofresources) are intended for the UE 115-b, and so forth.

A UE 115, such as the UE 115-a, may transmit a dedicated coordinationmessage 220 directly to an intended recipient (i.e., another UE 115,such as the UE 115-b or the UE 115-c), or may transmit a samecoordination message 220 to multiple UEs 115 (e.g., both the UE 115-band the UE 115-c). In some examples, a UE 115 may transmit a request forthe coordination message 220. The UEs 115 receiving a coordinationmessage 220 may determine (e.g., based on a destination identifier, anindication included in or associated with the coordination message 220,etc.) the intended recipient of the coordination message 220 and mayidentify the status of the respective one or more resources (e.g.,indicated in the coordination message 220) based on the intendedrecipient and the indicated respective preference statuses. As anexample, a coordination message 220 may indicate that a set of resourcesis preferred. The UE 115-a may transmit (e.g., via respective sidelinks210) the coordination message 220 to both of the UEs 115-b and 115-c,along with an indication that the intended recipient is the UE 115-b.The UEs 115-b and 115-c may receive the coordination message 220,determine the intended recipient, and assign statuses to the set ofresources accordingly. That is, the UE 115-b may identify that the setof resources are preferred (i.e., have a status of preferred) becausethe UE 115-b is the intended recipient, while the UE 115-c may identifythat the set of resources are non-preferred (e.g., because the UE 115-cis not the intended recipient). Alternatively, the coordination message220 may indicate that the set of resources is preferred for the UE 115-band non-preferred for the UE 115-c, and the UEs 115-b and 115-c mayidentify the respective statuses of the set of resources based on theindication.

In some implementations of the present disclosure, the UEs 115-b and115-c may be configured to utilize a coordination message 220 only ifthe respective UE 115 is the intended recipient. For example, the UE115-c may be dynamically configured or configured via an RRC message(such as a PC5-RRC message) to disregard the coordination message 220upon determining that the UE 115-b is the intended recipient (i.e., thatthe UE 115-c is not the intended recipient). In some cases, suchbehavior may be preconfigured, for example, per resource pool, percarrier, or per frequency band. In some examples, the coordinationmessage 220 or an associated SCI (e.g., SCI-2) may include an indicationthat the coordination message 220 is to be utilized only by the intendedrecipient.

In some examples, the UE 115-a may transmit dedicated coordinationmessages 220 to the UEs 115-b and 115-c for resources to be used insidelink communications between the UEs 115. As illustrated in FIG. 2 ,the UE 115-a may transmit a coordination message 220-a to the UE 115-bvia the sidelink 210-a and a coordination message 220-b to the UE 115-cvia the sidelink 210-b. The coordination message 220-a may includecoordination information for the UE 115-b and the coordination message220-b may include coordination information for the UE 115-c (i.e., thecontent of the coordination message 220-a may be different from thecoordination message 220-b). The UE 115-a may include, in the respectivecoordination messages 220, an explicit indication that the coordinationmessage 220-a is for the UE 115-b and that the coordination message220-b is for the UE 115-c.

Based on the coordination message 220-a, the UE 115-b may determine orotherwise identify a status (e.g., available, reserved, preferred,non-preferred) of one or more resources. For example, the UE 115-b maydetermine that the one or more resources are preferred based on theindication that the coordination message 220-a is for the UE 115-b.Additionally, or alternatively, the coordination message 220-a mayinclude an indication that the one or more resources are preferred,non-preferred, or some combination thereof for the UE 115-b, such thatthe UE 115-b may identify the status based on the indication. The UE115-b may select resources to use for transmitting, to the UE 115-a viathe sidelink 210-a, a sidelink transmission 215-a based on thedetermined status.

The UE 115-c may likewise determine or otherwise identify a status ofone or more resources based on the coordination message 220-b. If thecoordination message 220-b includes an indication that the one or moreresources are preferred or includes an indication that the UE 115-c isthe intended recipient, the UE 115-c may determine that the one or moreresources are preferred. If the coordination message 220-b includes anindication that the one or more resources are non-preferred or thatanother UE 115 is the intended recipient, the UE 115-c may determinethat the one or more resources are non-preferred. The UE 115-c may usethe determined status to select resources for transmitting, to the UE115-b via the sidelink 210-c, the sidelink transmission 215-b.

In some examples, the UEs 115-b and 115-c may determine or otherwiseidentify the status of the one or more resources based on an implicitassociation between the coordination messages 220 and one or more of theresources. For instance, the UE 115-b may transmit a request for thecoordination message 220-a on a first resource and may receive thecoordination message 220-a on a second resource. The UE 115-b maydetermine that the UE 115-b is the intended recipient of thecoordination message 220-a based on receiving the coordination message220-a on the second resource. As another example, the UE 115-b maydetermine that the UE 115-b is an intended recipient by identifying thatthe coordination message 220-a is associated with a process to reservethe one or more resources. The UE 115-b may determine the status of theone or more resources based on identifying that the UE 115-b is theintended recipient of the coordination message 220-a. Additionally, oralternatively, the coordination message 220-a may be received on aresource that is associated with a resource indicated in thecoordination message 220-a. For instance, the UE 115-b may receive thecoordination message 220-a on a first resource, and the coordinationmessage 220-a may indicate that a second resource is a preferredresource. The UE 115-b may identify the preferred resource based onidentifying an association between the first resource and the secondresource.

The UEs 115 may have one or more unicast connections with one anotherand may implement the techniques described herein to determine statusesfor resources associated with the one or more unicast connections. Forexample, the UE 115-b may have a first unicast connection with the UE115-a and a second unicast connection with the UE 115-c. The UE 115-bmay receive, from the UE 115-a, the coordination message 220-a thatindicates a preference status for resources associated with the firstunicast connection. The UE 115-b may identify that the resources arepreferred resources for the first unicast connection and may thereforefurther identify that the resources are non-preferred for the secondunicast connection; thus, the UE 115-b may use the resources fortransmitting to the UE 115-a on the first unicast connection and mayrefrain from using the resources for transmitting to the UE 115-c on thesecond unicast connection.

In some cases, the UE 115-b may have a third unicast connection that isalso with the UE 115-a (e.g., in addition to the first unicastconnection). In such cases, the coordination message 220-a may indicate(e.g., via a source identifier, a destination identifier, or both) thatboth the first unicast connection and the third unicast connection areto the same UE 115-a. The UE 115-b may determine that the resourcespreferred for the first unicast connection may also be preferred for thethird unicast connection, and the UE 115-a may refrain from transmittinga coordination message 220 for each respective unicast connection.Alternatively, the UE 115-b may determine that the resources preferredfor the unicast connection may be non-preferred for the third unicastconnection, for instance, if the third unicast connection is associatedwith communications of a lower priority than the first unicastconnection.

FIG. 3 illustrates an example of a resource mapping 300 that supports UEcoordination for sidelink in accordance with aspects of the presentdisclosure. In some examples, the resource mapping 300 may implementedby aspects of the wireless communications system 100 and the wirelesscommunications system 200, as described in FIGS. 1 and 2 . The resourcemapping 300 may be implemented by a UE (e.g., a UE 115) to supportcoordination messages in a sidelink communications system according tothe techniques described herein. For example, the resource mapping 300may be used by a UE to determine and select resources to use forsidelink communications using coordination information received in acoordination message.

The resource mapping 300 may include a resource selection timing 305,which may include a sensing window 310, a resource selection trigger315, and a resource selection window 320. The UE may monitor a controlchannel (e.g., a sidelink control channel) to receive and decode controlsignals during the sensing window 310. Upon receiving the resourceselection trigger 315 (e.g., a data packet received T_(proc,1) after theresource selection window 320 and T₁ before the resource selectionwindow 320), the UE may select and reserve resources within the resourceselection window 320 for sidelink communication with another UE, forinstance, based on sensing performed during the sensing window 310 andcoordination information received in a coordination message. The sensingwindow 310 may be configured to span a duration T₀ and the resourceselection window may be configured to span a duration T₂.

During the sensing window 310, the UE may perform channel sensing (e.g.,sidelink channel sensing) by decoding SCI to identify occupied oravailable sidelink resources, e.g., from a pool of sidelink resources.For example, the UE may receive SCI from multiple other UEs indicatingsidelink resources reserved by the respective UE. Based on the channelsensing procedure, the UE may determine which resources are reserved(e.g., from resource reservations indicated in SCI) and which resourcesare available.

According to the techniques described herein, the UE may identify astatus (e.g., available, preferred, non-preferred, conflicting, etc.)for each of the respective resources included in the resource selectionwindow 320 based on the channel sensing procedure and one or morereceived coordination messages. For example, the UE may identify that aresource is a reserved resource 330, a preferred resource 335, anon-preferred resource 340, or a conflicting resource 345. The UE maydetermine a set of one or more candidate resources, which may includethose identified as available during the sensing window 310 as well asthose identified as preferred based on one or more received coordinationmessages, from which to select one or more resources 325 in one or moretime slots of the resource selection window 320. The selected resources325 may be used for sidelink communications by the UE.

As described with reference to FIG. 2 , the UE may identify which of theresources are preferred resources 335, non-preferred resources 340, andconflicting resources 345, based on receiving one or more coordinationmessages that include coordination information. For example, the UE mayreceive a coordination message that indicates preferred resources 335,non-preferred resources 340, or some combination thereof, and the UE mayidentify the respective resources based on the indication(s). As anexample, the coordination message may include a bitmap of the resourceselection window 320, where each bit corresponds to a resource andindicates whether the resource is preferred or non-preferred.Additionally, or alternatively, the UE may receive a coordinationmessage that is intended for a different UE, and the UE may identify thenon-preferred resources 340 based on the UE not being the intendedrecipient of the coordination message.

In some examples, a coordination message may indicate that a resourceconflict is detected for one or more resources, and the UE may identifythe conflicting resources 345 based on the resource conflict indication.For example, a conflicting resource 345 may be a resource that isassociated with resource reservations of two (or more) UEs. If a firstUE transmits an indication of a resource reservation (e.g., as part ofSCI) that is missed by a second UE, the second UE may be unaware of theresource reservation and may select or reserve the same resource. Thus,a UE identifying one or more conflicting resources 345 may refrain fromselecting the conflicting resources 345 during the resource selectionwindow, may remove or change a reservation associated with a conflictingresource 345, or, if the conflict has already occurred, may retransmit amessage associated with a conflicting resource 345.

A given resource may be identified as having multiple statuses. Forexample, a reserved resource 330 may also be a non-preferred resource340 and/or a conflicting resource 345. That is, the UE may determinethat a resource is a reserved resource 330 based on the channel sensingprocedure, and the same resource may be indicated as a non-preferredresource 340 in a coordination message (i.e., the resource is indicatedas a non-preferred resource 340 because the resource is already reservedby another UE). Similarly, a selected resource 325 may also be apreferred resource 335; put another way, the UE may select a selectedresource 325 based on the resource also being a preferred resource 335.

The UE may determine the set of candidate resources based on identifyingthe status of each resource. For example, the UE may exclude reservedresources 330, non-preferred resources 340, and conflicting resources345 from the set of candidate resources such that the one or moreselected resources 325 are selected from the remaining resources (e.g.,of the resource selection window 320). In some examples, the UE mayexclude reserved resources 330, non-preferred resources 340, andconflicting resources 345 in an order, for instance, based on when thesensing window 310 occurs and when the coordination message(s) arereceived. For instance, the UE may first exclude reserved resources 330upon performing the channel sensing procedure during the sensing window310, and may then exclude non-preferred resources 340 and conflictingresources 345 based on receiving a coordination message (e.g., after thesensing window 310). Additionally, or alternatively, the UE may includeonly preferred resources 335 in the set of candidate resources, suchthat the one or more selected resources 325 are selected from thepreferred resources 335. The UE may select, from the set of candidateresources, one or more selected resources 325 in one or more slots ofthe resource selection window 320 to use for sidelink communications.

FIG. 4 illustrates an example of a wireless communications system 400that supports UE coordination for sidelink in accordance with aspects ofthe present disclosure. The wireless communications system 400 mayimplement aspects of the wireless communications systems 100 and 200.For example, the wireless communications system 400 may include a UE115-d, a UE 115-e, and a UE 115-f, which may be examples of thecorresponding devices described herein.

The UEs 115 may communicate with one another via sidelink communicationsover sidelink channels, which may support or be examples of unicastconnections. For instance, the UE 115-d may have a unicast connection410-a with the UE 115-e and the UE 115-e may have a unicast connection410-b with the UE 115-f. The UE 115-d and the UE 115-f may have twounicast connections with one another, a unicast connection 410-c and aunicast connection 410-d.

As described herein and with reference to FIG. 2 , the UEs 115 maytransmit and receive coordination messages 415 over the correspondingunicast connections 410 and may identify a status of one or morecommunication resources for the sidelink communications based onreceiving the coordination messages 415. In some examples, the UE 115-dmay be designated (e.g., by a network) to generate and transmitcoordination messages 415-a, 415-c, and 415-d to the corresponding UEs115-e and 115-f, while in other examples, each of the UEs 115 maygenerate and transmit a coordination message 415. In some cases, the UE115-e, the UE 115-f, or both may transmit, to the UE 115-d, a messagerequesting a coordination message 415, and the UE 115-d may transmitcoordination messages 415 to the UEs 115-e and/or 115-f in response.

In the example of FIG. 4 , the coordination messages 415 may includecoordination information (e.g., a preference status) for communicationresources associated with one or more of the unicast connections 410. Insome cases, a coordination message 415 may include or may be associatedwith an indication of a source identifier associated with thetransmitting UE 115, a destination identifier associated with thereceiving UE 115, one or more of the associated unicast connections 410,or some combination thereof, that a UE 115 may use to identify theassociation between the communication resources and a unicast connection410. For example, the coordination message 415-a transmitted from the UE115-d to the UE 115-e may include an indication of a source identifier(e.g., associated with the UE 115-d), a destination identifier (e.g.,associated with the UE 115-e), and/or an indication of the unicastconnection 410-a. The coordination message 415-b, transmitted from theUE 115-e to the UE 115-f, may include an indication of a sourceidentifier associated with the UE 115-e, a destination identifierassociated with the UE 115-f, and an indication of the unicastconnection 410-b. The coordination messages 415-c and 415-d may bothinclude an indication of a source identifier associated with the UE115-d and a destination identifier associated with the UE 115-f, but thecoordination message 415-c may include an indication of the unicastconnection 410-c, while the coordination message 415-d may include anindication of the unicast connection 410-d. In some cases, thecoordination messages 415 may be associated with respective SCI-2messages, and the SCI-2 messages may include an indication of the sourceidentifier(s), destination identifier(s), unicast connectionidentifier(s), or some combination thereof. In such cases, acoordination message 415 may be implicitly associated with the indicatedidentifiers via the association with the respective SCI-2 message.

The unicast connection 410 associated with the resources indicated inthe coordination messages 415 may be considered by a UE 115 when the UE115 identifies the status of one or more resources. For example, the UE115-e may receive the coordination message 415-a, which may indicatethat one or more resources are preferred for the unicast connection410-a. The UE 115-e may therefore identify that the one or moreresources are non-preferred for the unicast connection 410-b. That is,because the UE 115-e has identified that the one or more resources arepreferred for the unicast connection 410-a, the one or more resourcesmay not be available for or may cause interference if used on theunicast connection 410-b, and may therefore be considered non-preferredfor the unicast connection 410-b.

The UE 115-f may identify the status of one or more resources associatedwith the unicast connections 410-b, 410-c, and 410-d based on thereceived coordination messages 415-b, 415-c, and 415-d, respectively orin combination with one another. For example, the UE 115-f may determine(e.g., based on indications included in the coordination message 415-cand the coordination message 415-d, respectively) that the unicastconnection 410-c and the unicast connection 410-d are both associatedwith the UE 115-d. The UE 115-f may be configured to determine that acoordination message 415 associated with one of the unicast connections410-c or 410-d may be utilized for the other unicast connection 410-c or410-d, for example, based on both of the unicast connections 410-c and410-d being associated with the same UE 115-d (e.g., with the samesource identifier). The coordination message 415-c may indicate that oneor more resources are preferred resources for the unicast connection410-c, and the UE 115-f may determine that the one or more resources arealso preferred resources for the unicast connection 410-d.

Additionally, the UE 115-f may determine that the one or more resourcesidentified and/or indicated as preferred for the unicast connections410-c and 410-d are non-preferred for the unicast connection 410-b, forexample, based on the unicast connection 410-b being between the UE115-f and the UE 115-e. In some cases, the UE 115-f may determinepreferred resources for the unicast connection 410-b based on apreference status included in the coordination message 415-b. Thepreferred resources for the unicast connection 410-b may further beidentified by the UE 115-f as being non-preferred for the unicastconnection 410-c and/or the unicast connection 410-d.

Alternatively, in some examples, the UE 115-f may determine thatresources indicated or identified as preferred for one unicastconnection 410 between the UE 115-f and the UE 115-d are non-preferredfor the other unicast connection 410 between the UE 115-f and the UE115-d. The UE 115-f may identify that one or more resources arepreferred for the unicast connection 410-c, for example, based on anindication included in the coordination message 415-c. The one or moreresources may be identified by the UE 115-f as being non-preferred forthe unicast connection 410-d. Likewise, the coordination message 415-dmay indicate that one or more resources are preferred for the unicastconnection 410-d, and the UE 115-f may determine that the one or moreresources are non-preferred for the unicast connection 410-c.

Each of the UEs 115-d, 115-e, and 115-f may select one or more resources(e.g., as described with reference to FIG. 3 ) for sidelinkcommunications for corresponding unicast connections 410 based onidentifying the status of one or more resources. For example, the UE115-f may select resources, for a transmission to the UE 115-d using theunicast connection 410-c, that were identified as preferred for theunicast connection 410-c and may refrain from selecting resources thatwere indicated as non-preferred for the unicast connection 410-c or wereindicated as preferred for another unicast connection 410.

FIG. 5 illustrates an example of a process flow 500 that supports UEcoordination for sidelink in accordance with aspects of the presentdisclosure. In some examples, the process flow 500 may implement aspectsof wireless communications systems 100, 200, or 400. For example,process flow 500 may include a UE 115-g, UE 115-h, and UE 115-i, whichmay be examples of corresponding wireless devices as described herein.In the following description of the process flow 500, the operationsbetween the UEs 115 may be transmitted in a different order than theexemplary order shown, or the operations performed by the UEs 115 may beperformed in different orders or at different times. Some operations mayalso be left out of the process flow 500, or other operations may beadded to the process flow 500. While the UEs 115 are shown performingoperations of process flow 500, any wireless device may perform theoperations shown.

The UEs 115 illustrated in FIG. 5 may communicate with one another viaone or more sidelink channels. For example, the UEs 115 use sensing andresource selection processes as described with reference to FIG. 3 andmay transmit and receive sidelink communications. In some examples, theUEs 115 may communicate using one or more unicast connections with oneor more other UEs 115. As described herein, the UEs 115 may utilizecoordination messages to determine or otherwise identify a status of oneor more communication resources, where the status may indicate whether arespective communication resource is preferred, non-preferred,available, or unavailable. The UEs 115 may select one or morecommunication resources for the sidelink communications based on theidentified status(es).

At 505, the UE 115-g may transmit a request message to the UE 115-h torequest a coordination message for the sidelink communications betweenthe UEs 115.

At 510, the UE 115-h may generate and transmit a coordination message toboth of the UE 115-g and the UE 115-i. The coordination message may beincluded as part of an RRC message, a MAC-CE, an SCI-1, or an SCI-2. Thecoordination message may indicate a preference status of one or morecommunication resources for the sidelink communications. The preferencestatus may indicate whether a respective communication resource ispreferred or non-preferred. In some cases, the coordination message mayindicate whether a resource conflict for the one or more communicationresources is detected; the resource conflict may be indicated by a NACKassociated with a message transmitted by a scheduling UE of the sidelinkcommunications. In some examples, the UE 115-h may transmit thecoordination message to the UE 115-g based on receiving the requestmessage at 505.

At 515-a, the UE 115-g may identify an intended recipient of thecoordination message, i.e., the UE 115-g may identify whether the UE115-g is an intended recipient of the coordination message. In someexamples, the coordination message may include an indication of theintended recipient. In some cases, the UE 115-g may identify an intendedrecipient of the coordination message by identifying a destinationidentifier included in the coordination message. In some examples, thecoordination message may be associated with the destination identifier,for example, if the destination identifier is included in SCI (e.g.,SCI-2) associated with the coordination message. In some cases, the UE115-g may identify whether the UE 115-g is an intended recipient of thecoordination message by determining that the coordination message isassociated with a process to reserve the communication resources for thesidelink communications.

At 515-b, the UE 115-i may likewise identify whether the UE 115-i is anintended recipient of the coordination message, for example, based on anindication of the intended recipient (e.g., a destination identifier)included in the coordination message or in SCI associated with thecoordination message.

At 520, the UE 115-g may identify one or more communication connectionsassociated with the communication resources. For example, the UE 115-gmay determine that the communication resources are associated with afirst unicast connection between the UE 115-g and the UE 115-h. In someexamples, the coordination message received at 510 may include anindication of the first unicast connection, an indication of a secondunicast connection, or both. In some cases, the coordination message mayinclude an indication of a source identifier and a destinationidentifier, and the UE 115-g may identify the first unicast connection,the second unicast connection, or both based on the source identifierand the destination identifier.

At 525-a, the UE 115-g may identify a status of one or more of thecommunication resources, for example, based on the coordination messagereceived at 510. The identified status may indicate whether a respectivecommunication resource is available, reserved, preferred, non-preferred,or some combination thereof. In some examples, the UE 115-g may identifythat one or more communication resources are preferred or non-preferredbased on the respective preference status of the resource indicated inthe coordination message.

Additionally, or alternatively, the UE 115-g may identify the status ofone or more of the communication resources based on the intendedrecipient identified at 515-a. For example, the UE 115-g may identifythe status of the one or more communication resources based ondetermining, at 515-a, that the UE 115-g is the intended recipient ofthe coordination message; alternatively, the UE 115-g may identify thestatus based on determining (e.g., at 515-a) that the UE 115-g is notthe intended recipient of the coordination message. In some examples,the UE 115-g may identify that the one or more communication resourcesare preferred based on the UE 115-g being the intended recipient.

In some examples, the UE 115-g may identify the status of one or more ofthe communication resources based on a combination of identifying theintended recipient and identifying the preference status of the one ormore communication resources indicated in the coordination message. Forexample, the coordination message may indicate that the one or morecommunication resources are preferred or non-preferred. If, at 515-a,the UE 115-g is identified as the intended recipient, the UE 115-g may,at 525-a, identify the status of the one or more communication resourcesas corresponding to the preference status indicated in the coordinationmessage. That is, if the coordination message indicates that the one ormore communication resources are preferred and the UE 115-g is theintended recipient, the UE 115-g may identify that the one or morecommunication resources are preferred resources; if the coordinationmessage indicates that the one or more communication resources arenon-preferred and the UE 115-g is the intended recipient, the UE 115-gmay identify that the one or more communication resources arenon-preferred.

However, if the UE 115-g is not the intended recipient, the UE 115-gmay, at 525-a, identify the status of the one or more communicationresources as being the opposite of the preference status indicated inthe coordination message. For example, if the coordination messageindicates that the one or more communication resources are preferred butthe UE 115-g is not the intended recipient, the UE 115-g may determinethat the one or more communication resources are non-preferredresources.

In some examples, the UE 115-g may identify the status of the one ormore communication resources based on the one or more associatedcommunication connections (e.g., identified at 520 and/or indicated inthe coordination message). For example, the UE 115-g may identify thatthe one or more communication resources are associated with andpreferred for the first unicast connection with the UE 115-h.Additionally, in some cases, the UE 115-g may identify a status of oneor more other communication resources associated with a second unicastconnection with the UE 115-h, where the one or more other communicationresources associated with the second unicast connection correspond tothe one or more communication resources associated with the firstunicast connection. For example, if the one or more communicationresources associated with the first unicast connection are identified(e.g., by the UE 115-g) as preferred, the one or more othercommunication resources associated with the second unicast connectionmay likewise be identified (e.g., by the UE 115-g) as preferred.Alternatively, if the one or more communication resources associatedwith the first unicast connection are identified as preferred, the oneor more other resources associated with the second unicast connectionmay be identified as non-preferred.

In some examples, the UE 115-g may identify a status of one or morecommunication resources associated with a third unicast connection witha UE 115 different from the UE 115-h, where the one or morecommunication resources associated with the third unicast connectioncorrespond to the one or more communication resources associated withthe first unicast connection. The UE 115-g may identify that the one ormore communication resources associated with the third unicastconnection are non-preferred resources, for instance, based onidentifying that the one or more communication resources associated withthe first unicast connection are preferred resources.

At 525-b, the UE 115-i may likewise identify a status of one or more ofthe communication resources, for example, based on the coordinationmessage received at 510. In some examples, the UE 115-g may identifythat one or more communication resources are preferred or non-preferredbased on the respective preference status of the resource indicated inthe coordination message, the intended recipient identified at 515-b, orsome combination thereof. In the example of FIG. 5 , the UE 115-i mayidentify, at 515-b, that the UE 115-i is not the intended recipient ofthe coordination message. The UE 115-i may identify that thecoordination message indicates that the one or more communicationresources are preferred resources. The UE 115-i may therefore identifythat the one or more communication resources are non-preferred for theUE 115-i.

At 530-a, the UE 115-g may select one or more communication resources ofthe one or more communication resources for the sidelink communicationsbased on the status(es) identified at 525-a. For example, the UE 115-gmay select a communication resource from the identified preferredresources to transmit a sidelink transmission. In some examples, the UE115-g may refrain from selecting a communication resource from theidentified non-preferred resources.

At 530-b, the UE 115-i may likewise select one or more communicationresources of the one or more communication resources for the sidelinkcommunications based on the status(es) identified at 525-b. For example,the UE 115-i may select a communication resource from the identifiedpreferred resources to transmit a sidelink transmission and may refrainfrom selecting a communication resource from the identifiednon-preferred resources.

At 535, the UE 115-g may transmit a sidelink transmission to the UE115-h using the resources selected at 530-a. Similarly, at 540, the UE115-h may transmit a sidelink transmission to the UE 115-h using theresources selected at 530-b.

FIG. 6 shows a block diagram 600 of a device 605 that supports UEcoordination for sidelink in accordance with aspects of the presentdisclosure. The device 605 may be an example of aspects of a UE 115 asdescribed herein. The device 605 may include a receiver 610, atransmitter 615, and a communications manager 620. The device 605 mayalso include a processor. Each of these components may be incommunication with one another (e.g., via one or more buses).

The receiver 610 may provide a means for receiving information such aspackets, user data, control information, or any combination thereofassociated with various information channels (e.g., control channels,data channels, information channels related to UE coordination forsidelink). Information may be passed on to other components of thedevice 605. The receiver 610 may utilize a single antenna or a set ofmultiple antennas.

The transmitter 615 may provide a means for transmitting signalsgenerated by other components of the device 605. For example, thetransmitter 615 may transmit information such as packets, user data,control information, or any combination thereof associated with variousinformation channels (e.g., control channels, data channels, informationchannels related to UE coordination for sidelink). In some examples, thetransmitter 615 may be co-located with a receiver 610 in a transceivermodule. The transmitter 615 may utilize a single antenna or a set ofmultiple antennas.

The communications manager 620, the receiver 610, the transmitter 615,or various combinations thereof or various components thereof may beexamples of means for performing various aspects of UE coordination forsidelink as described herein. For example, the communications manager620, the receiver 610, the transmitter 615, or various combinations orcomponents thereof may support a method for performing one or more ofthe functions described herein.

In some examples, the communications manager 620, the receiver 610, thetransmitter 615, or various combinations or components thereof may beimplemented in hardware (e.g., in communications management circuitry).The hardware may include a processor, a digital signal processor (DSP),an application-specific integrated circuit (ASIC), a field-programmablegate array (FPGA) or other programmable logic device, a discrete gate ortransistor logic, discrete hardware components, or any combinationthereof configured as or otherwise supporting a means for performing thefunctions described in the present disclosure. In some examples, aprocessor and memory coupled with the processor may be configured toperform one or more of the functions described herein (e.g., byexecuting, by the processor, instructions stored in the memory).

Additionally or alternatively, in some examples, the communicationsmanager 620, the receiver 610, the transmitter 615, or variouscombinations or components thereof may be implemented in code (e.g., ascommunications management software or firmware) executed by a processor.If implemented in code executed by a processor, the functions of thecommunications manager 620, the receiver 610, the transmitter 615, orvarious combinations or components thereof may be performed by ageneral-purpose processor, a DSP, a central processing unit (CPU), anASIC, an FPGA, or any combination of these or other programmable logicdevices (e.g., configured as or otherwise supporting a means forperforming the functions described in the present disclosure).

In some examples, the communications manager 620 may be configured toperform various operations (e.g., receiving, monitoring, transmitting)using or otherwise in cooperation with the receiver 610, the transmitter615, or both. For example, the communications manager 620 may receiveinformation from the receiver 610, send information to the transmitter615, or be integrated in combination with the receiver 610, thetransmitter 615, or both to receive information, transmit information,or perform various other operations as described herein.

The communications manager 620 may support wireless communications at afirst UE in accordance with examples as disclosed herein. For example,the communications manager 620 may be configured as or otherwise supporta means for receiving, from a second UE, a coordination message over asidelink channel that indicates a preference status of communicationresources for sidelink communications between two or more UEs. Thecommunications manager 620 may be configured as or otherwise support ameans for identifying a status of one or more communication resourcesfor the sidelink communications based on the received coordinationmessage, where the identified status of each communication resource ofthe one or more communication resources indicates whether a respectivecommunication resource is available, reserved, preferred, ornon-preferred, or a combination thereof. The communications manager 620may be configured as or otherwise support a means for selecting acommunication resource for the sidelink communications based on theidentified status of the one or more communication resources.

By including or configuring the communications manager 620 in accordancewith examples as described herein, the device 605 (e.g., a processorcontrolling or otherwise coupled to the receiver 610, the transmitter615, the communications manager 620, or a combination thereof) maysupport techniques for more efficiently utilizing sidelink resources insidelink communications. Including an indication of a preference statusof communication resources in a coordination message may enable thedevice 605 to avoid resources that may cause a conflict with anotherdevice, thereby avoiding latency and increasing communicationsreliability. Further, by determining a preference status based onwhether the device 605 is an intended recipient of the coordinationmessage, the device 605 may transmit and/or receive fewer overallcoordination messages.

FIG. 7 shows a block diagram 700 of a device 705 that supports UEcoordination for sidelink in accordance with aspects of the presentdisclosure. The device 705 may be an example of aspects of a device 605or a UE 115 as described herein. The device 705 may include a receiver710, a transmitter 715, and a communications manager 720. The device 705may also include a processor. Each of these components may be incommunication with one another (e.g., via one or more buses).

The receiver 710 may provide a means for receiving information such aspackets, user data, control information, or any combination thereofassociated with various information channels (e.g., control channels,data channels, information channels related to UE coordination forsidelink). Information may be passed on to other components of thedevice 705. The receiver 710 may utilize a single antenna or a set ofmultiple antennas.

The transmitter 715 may provide a means for transmitting signalsgenerated by other components of the device 705. For example, thetransmitter 715 may transmit information such as packets, user data,control information, or any combination thereof associated with variousinformation channels (e.g., control channels, data channels, informationchannels related to UE coordination for sidelink). In some examples, thetransmitter 715 may be co-located with a receiver 710 in a transceivermodule. The transmitter 715 may utilize a single antenna or a set ofmultiple antennas.

The device 705, or various components thereof, may be an example ofmeans for performing various aspects of UE coordination for sidelink asdescribed herein. For example, the communications manager 720 mayinclude a coordination message component 725, a resource statuscomponent 730, a scheduling component 735, or any combination thereof.The communications manager 720 may be an example of aspects of acommunications manager 620 as described herein. In some examples, thecommunications manager 720, or various components thereof, may beconfigured to perform various operations (e.g., receiving, monitoring,transmitting) using or otherwise in cooperation with the receiver 710,the transmitter 715, or both. For example, the communications manager720 may receive information from the receiver 710, send information tothe transmitter 715, or be integrated in combination with the receiver710, the transmitter 715, or both to receive information, transmitinformation, or perform various other operations as described herein.

The communications manager 720 may support wireless communications at afirst UE in accordance with examples as disclosed herein. Thecoordination message component 725 may be configured as or otherwisesupport a means for receiving, from a second UE, a coordination messageover a sidelink channel that indicates a preference status ofcommunication resources for sidelink communications between two or moreUEs. The resource status component 730 may be configured as or otherwisesupport a means for identifying a status of one or more communicationresources for the sidelink communications based on the receivedcoordination message, where the identified status of each communicationresource of the one or more communication resources indicates whether arespective communication resource is available, reserved, preferred, ornon-preferred, or a combination thereof. The scheduling component 735may be configured as or otherwise support a means for selecting acommunication resource for the sidelink communications based on theidentified status of the one or more communication resources.

FIG. 8 shows a block diagram 800 of a communications manager 820 thatsupports UE coordination for sidelink in accordance with aspects of thepresent disclosure. The communications manager 820 may be an example ofaspects of a communications manager 620, a communications manager 720,or both, as described herein. The communications manager 820, or variouscomponents thereof, may be an example of means for performing variousaspects of UE coordination for sidelink as described herein. Forexample, the communications manager 820 may include a coordinationmessage component 825, a resource status component 830, a schedulingcomponent 835, an intended recipient component 840, or any combinationthereof. Each of these components may communicate, directly orindirectly, with one another (e.g., via one or more buses).

The communications manager 820 may support wireless communications at afirst UE in accordance with examples as disclosed herein. Thecoordination message component 825 may be configured as or otherwisesupport a means for receiving, from a second UE, a coordination messageover a sidelink channel that indicates a preference status ofcommunication resources for sidelink communications between two or moreUEs. The resource status component 830 may be configured as or otherwisesupport a means for identifying a status of one or more communicationresources for the sidelink communications based on the receivedcoordination message, where the identified status of each communicationresource of the one or more communication resources indicates whether arespective communication resource is available, reserved, preferred, ornon-preferred, or a combination thereof. The scheduling component 835may be configured as or otherwise support a means for selecting acommunication resource for the sidelink communications based on theidentified status of the one or more communication resources.

In some examples, to support identifying the status, the resource statuscomponent 830 may be configured as or otherwise support a means foridentifying that the one or more communication resources are preferredfor the sidelink communications between the two or more UEs or the oneor more communication resources are non-preferred for the sidelinkcommunications between the two or more UEs, where the preference statusindicates whether the one or more communication resources are preferredor non-preferred for the sidelink communications between the two or moreUEs.

In some examples, the scheduling component 835 may be configured as orotherwise support a means for transmitting a message requesting thecoordination message for the sidelink communications, where receivingthe coordination message is based on transmitting the message.

In some examples, the intended recipient component 840 may be configuredas or otherwise support a means for identifying whether the first UE isan intended recipient of the coordination message, where identifying thestatus of the one or more communication resources is based onidentifying whether the first UE is the intended recipient of thecoordination message.

In some examples, the coordination message component 825 may beconfigured as or otherwise support a means for identifying whether thecoordination message indicates preferred resources or non-preferredresources, where identifying the status of the one or more communicationresources is based on identifying whether the first UE is the intendedrecipient of the coordination message and identifying whether thecoordination message indicates the preferred resources or thenon-preferred resources.

In some examples, to support identifying the status, the resource statuscomponent 830 may be configured as or otherwise support a means foridentifying that the communication resource is a preferred resourcebased on the first UE being the intended recipient and the coordinationmessage indicating the preferred resources. In some examples, to supportidentifying the status, the resource status component 830 may beconfigured as or otherwise support a means for identifying that thecommunication resource is a non-preferred resource based on a third UEbeing the intended recipient and the coordination message indicating thepreferred resources. In some examples, to support identifying thestatus, the resource status component 830 may be configured as orotherwise support a means for identifying that the communicationresource is a non-preferred resource based on the first UE being theintended recipient and the coordination message indicating thenon-preferred resources.

In some examples, the coordination message includes an indication of theintended recipient. In some examples, the intended recipient component840 may be configured as or otherwise support a means for identifying adestination identifier included in or associated with the coordinationmessage, where identifying whether the first UE is the intendedrecipient of the coordination message is based on identifying thedestination identifier.

In some examples, the destination identifier is included in sidelinkcontrol information associated with the coordination message.

In some examples, identifying whether the first UE is the intendedrecipient of the coordination message is based on the coordinationmessage being associated with a process to reserve the communicationresource for the sidelink communications.

In some examples, the coordination message includes a portion of an RRCmessage, a portion of a MAC-CE, a portion of a first-stage SCI, or aportion of a second-stage SCI.

In some examples, the one or more communication resources for thesidelink communications are associated with a first unicastcommunication connection between the first UE and the second UE. In someexamples, to support identifying the status, the resource statuscomponent 830 may be configured as or otherwise support a means foridentifying that the one or more communication resources are preferredresources of the first unicast communication connection based onreceiving the coordination message.

In some examples, the resource status component 830 may be configured asor otherwise support a means for identifying that a second communicationresource of a second unicast communication connection between the firstUE and the second UE is a preferred resource based on receiving thecoordination message for the first unicast communication connection, thesecond communication resource corresponding to one of the one or morecommunication resources of the first unicast communication connection.

In some examples, the resource status component 830 may be configured asor otherwise support a means for identifying that a second communicationresource of a second unicast communication connection between the firstUE and the second UE is a non-preferred resource based on receiving thecoordination message for the first unicast communication connection thatindicates that the one or more communication resources are the preferredresources, the second communication resource corresponding to one of theone or more communication resources of the first unicast communicationconnection.

In some examples, the resource status component 830 may be configured asor otherwise support a means for identifying that a second communicationresource of a second unicast communication connection between the firstUE and a third UE is a non-preferred resource based on receiving thecoordination message for the first unicast communication connection thatindicates that the one or more communication resources are the preferredresources, the second communication resource corresponding to one of theone or more communication resources of the first unicast communicationconnection.

In some examples, the coordination message indicates a source identifierand a destination identifier, and the coordination message component 825may be configured as or otherwise support a means for identifying thefirst unicast communication connection based on the source identifierand the destination identifier.

In some examples, the coordination message includes a first indicationof the first unicast communication connection and a second indication ofa second unicast communication connection. In some examples, thecoordination message indicates whether a resource conflict for the oneor more communication resources for the sidelink communications isdetected. In some examples, an indication of the resource conflictincludes a NACK associated with a message transmitted by a scheduling UEof the sidelink communications.

FIG. 9 shows a diagram of a system 900 including a device 905 thatsupports UE coordination for sidelink in accordance with aspects of thepresent disclosure. The device 905 may be an example of or include thecomponents of a device 605, a device 705, or a UE 115 as describedherein. The device 905 may communicate wirelessly with one or more basestations 105, UEs 115, or any combination thereof. The device 905 mayinclude components for bi-directional voice and data communicationsincluding components for transmitting and receiving communications, suchas a communications manager 920, an input/output (I/O) controller 910, atransceiver 915, an antenna 925, a memory 930, code 935, and a processor940. These components may be in electronic communication or otherwisecoupled (e.g., operatively, communicatively, functionally,electronically, electrically) via one or more buses (e.g., a bus 945).

The I/O controller 910 may manage input and output signals for thedevice 905. The I/O controller 910 may also manage peripherals notintegrated into the device 905. In some cases, the I/O controller 910may represent a physical connection or port to an external peripheral.In some cases, the I/O controller 910 may utilize an operating systemsuch as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, oranother known operating system. Additionally or alternatively, the I/Ocontroller 910 may represent or interact with a modem, a keyboard, amouse, a touchscreen, or a similar device. In some cases, the I/Ocontroller 910 may be implemented as part of a processor, such as theprocessor 940. In some cases, a user may interact with the device 905via the I/O controller 910 or via hardware components controlled by theI/O controller 910.

In some cases, the device 905 may include a single antenna 925. However,in some other cases, the device 905 may have more than one antenna 925,which may be capable of concurrently transmitting or receiving multiplewireless transmissions. The transceiver 915 may communicatebi-directionally, via the one or more antennas 925, wired, or wirelesslinks as described herein. For example, the transceiver 915 mayrepresent a wireless transceiver and may communicate bi-directionallywith another wireless transceiver. The transceiver 915 may also includea modem to modulate the packets, to provide the modulated packets to oneor more antennas 925 for transmission, and to demodulate packetsreceived from the one or more antennas 925. The transceiver 915, or thetransceiver 915 and one or more antennas 925, may be an example of atransmitter 615, a transmitter 715, a receiver 610, a receiver 710, orany combination thereof or component thereof, as described herein.

The memory 930 may include random access memory (RAM) and read-onlymemory (ROM). The memory 930 may store computer-readable,computer-executable code 935 including instructions that, when executedby the processor 940, cause the device 905 to perform various functionsdescribed herein. The code 935 may be stored in a non-transitorycomputer-readable medium such as system memory or another type ofmemory. In some cases, the code 935 may not be directly executable bythe processor 940 but may cause a computer (e.g., when compiled andexecuted) to perform functions described herein. In some cases, thememory 930 may contain, among other things, a basic I/O system (BIOS)which may control basic hardware or software operation such as theinteraction with peripheral components or devices.

The processor 940 may include an intelligent hardware device (e.g., ageneral-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, anFPGA, a programmable logic device, a discrete gate or transistor logiccomponent, a discrete hardware component, or any combination thereof).In some cases, the processor 940 may be configured to operate a memoryarray using a memory controller. In some other cases, a memorycontroller may be integrated into the processor 940. The processor 940may be configured to execute computer-readable instructions stored in amemory (e.g., the memory 930) to cause the device 905 to perform variousfunctions (e.g., functions or tasks supporting UE coordination forsidelink). For example, the device 905 or a component of the device 905may include a processor 940 and memory 930 coupled to the processor 940,the processor 940 and memory 930 configured to perform various functionsdescribed herein.

The communications manager 920 may support wireless communications at afirst UE in accordance with examples as disclosed herein. For example,the communications manager 920 may be configured as or otherwise supporta means for receiving, from a second UE, a coordination message over asidelink channel that indicates a preference status of communicationresources for sidelink communications between two or more UEs. Thecommunications manager 920 may be configured as or otherwise support ameans for identifying a status of one or more communication resourcesfor the sidelink communications based on the received coordinationmessage, where the identified status of each communication resource ofthe one or more communication resources indicates whether a respectivecommunication resource is available, reserved, preferred, ornon-preferred, or a combination thereof. The communications manager 920may be configured as or otherwise support a means for selecting acommunication resource for the sidelink communications based on theidentified status of the one or more communication resources.

By including or configuring the communications manager 920 in accordancewith examples as described herein, the device 905 may support techniquesfor more efficiently utilizing sidelink resources in sidelinkcommunications. Enabling the device 905 and other devices to receive asame coordination message and determine a preference status ofcommunication resources may improve coordination among the devices(e.g., including the device 905), which may in turn reduce latency andincrease communications reliability. Further, fewer coordinationmessages overall may be transmitted or received by the device 905, whichmay increase efficiency of the system.

In some examples, the communications manager 920 may be configured toperform various operations (e.g., receiving, monitoring, transmitting)using or otherwise in cooperation with the transceiver 915, the one ormore antennas 925, or any combination thereof. Although thecommunications manager 920 is illustrated as a separate component, insome examples, one or more functions described with reference to thecommunications manager 920 may be supported by or performed by theprocessor 940, the memory 930, the code 935, or any combination thereof.For example, the code 935 may include instructions executable by theprocessor 940 to cause the device 905 to perform various aspects of UEcoordination for sidelink as described herein, or the processor 940 andthe memory 930 may be otherwise configured to perform or support suchoperations.

FIG. 10 shows a flowchart illustrating a method 1000 that supports UEcoordination for sidelink in accordance with aspects of the presentdisclosure. The operations of the method 1000 may be implemented by a UEor its components as described herein. For example, the operations ofthe method 1000 may be performed by a UE 115 as described with referenceto FIGS. 1 through 9 . In some examples, a UE may execute a set ofinstructions to control the functional elements of the UE to perform thedescribed functions. Additionally or alternatively, the UE may performaspects of the described functions using special-purpose hardware.

At 1005, the method may include receiving, from a second UE, acoordination message over a sidelink channel that indicates a preferencestatus of communication resources for sidelink communications betweentwo or more UEs. The operations of 1005 may be performed in accordancewith examples as disclosed herein. In some examples, aspects of theoperations of 1005 may be performed by a coordination message component825 as described with reference to FIG. 8 .

At 1010, the method may include identifying a status of one or morecommunication resources for the sidelink communications based on thereceived coordination message, where the identified status of eachcommunication resource of the one or more communication resourcesindicates whether a respective communication resource is available,reserved, preferred, or non-preferred, or a combination thereof. Theoperations of 1010 may be performed in accordance with examples asdisclosed herein. In some examples, aspects of the operations of 1010may be performed by a resource status component 830 as described withreference to FIG. 8 .

At 1015, the method may include selecting a communication resource forthe sidelink communications based on the identified status of the one ormore communication resources. The operations of 1015 may be performed inaccordance with examples as disclosed herein. In some examples, aspectsof the operations of 1015 may be performed by a scheduling component 835as described with reference to FIG. 8 .

FIG. 11 shows a flowchart illustrating a method 1100 that supports UEcoordination for sidelink in accordance with aspects of the presentdisclosure. The operations of the method 1100 may be implemented by a UEor its components as described herein. For example, the operations ofthe method 1100 may be performed by a UE 115 as described with referenceto FIGS. 1 through 9 . In some examples, a UE may execute a set ofinstructions to control the functional elements of the UE to perform thedescribed functions. Additionally or alternatively, the UE may performaspects of the described functions using special-purpose hardware.

At 1105, the method may include receiving, from a second UE, acoordination message over a sidelink channel that indicates a preferencestatus of communication resources for sidelink communications betweentwo or more UEs. The operations of 1105 may be performed in accordancewith examples as disclosed herein. In some examples, aspects of theoperations of 1105 may be performed by a coordination message component825 as described with reference to FIG. 8 .

At 1110, the method may include identifying whether the first UE is anintended recipient of the coordination message. The operations of 1110may be performed in accordance with examples as disclosed herein. Insome examples, aspects of the operations of 1110 may be performed by anintended recipient component 840 as described with reference to FIG. 8 .

At 1115, the method may include identifying whether the coordinationmessage indicates preferred resources or non-preferred resources, Theoperations of 1115 may be performed in accordance with examples asdisclosed herein. In some examples, aspects of the operations of 1115may be performed by a coordination message component 825 as describedwith reference to FIG. 8 .

At 1120, the method may include identifying a status of one or morecommunication resources for the sidelink communications based on thereceived coordination message, where the identified status of eachcommunication resource of the one or more communication resourcesindicates whether a respective communication resource is available,reserved, preferred, or non-preferred, or a combination thereof, andwhere identifying the status of the one or more communication resourcesis based on identifying whether the first UE is the intended recipientof the coordination message and identifying whether the coordinationmessage indicates the preferred resources or the non-preferredresources. The operations of 1120 may be performed in accordance withexamples as disclosed herein. In some examples, aspects of theoperations of 1120 may be performed by a resource status component 830as described with reference to FIG. 8 .

At 1125, the method may include selecting a communication resource forthe sidelink communications based on the identified status of the one ormore communication resources. The operations of 1125 may be performed inaccordance with examples as disclosed herein. In some examples, aspectsof the operations of 1125 may be performed by a scheduling component 835as described with reference to FIG. 8 .

FIG. 12 shows a flowchart illustrating a method 1200 that supports UEcoordination for sidelink in accordance with aspects of the presentdisclosure. The operations of the method 1200 may be implemented by a UEor its components as described herein. For example, the operations ofthe method 1200 may be performed by a UE 115 as described with referenceto FIGS. 1 through 9 . In some examples, a UE may execute a set ofinstructions to control the functional elements of the UE to perform thedescribed functions. Additionally or alternatively, the UE may performaspects of the described functions using special-purpose hardware.

At 1205, the method may include receiving, from a second UE, acoordination message over a sidelink channel that indicates a preferencestatus of communication resources for sidelink communications betweentwo or more UEs. The operations of 1205 may be performed in accordancewith examples as disclosed herein. In some examples, aspects of theoperations of 1205 may be performed by a coordination message component825 as described with reference to FIG. 8 .

At 1210, the method may include identifying a status of one or morecommunication resources for the sidelink communications based on thereceived coordination message, where the identified status of eachcommunication resource of the one or more communication resourcesindicates whether a respective communication resource is available,reserved, preferred, or non-preferred, or a combination thereof, andwhere the one or more communication resources for the sidelinkcommunications are associated with a first unicast communicationconnection between the first UE and the second UE. The operations of1210 may be performed in accordance with examples as disclosed herein.In some examples, aspects of the operations of 1210 may be performed bya resource status component 830 as described with reference to FIG. 8 .

At 1215, the method may include identifying that the one or morecommunication resources are preferred resources of the first unicastcommunication connection based on receiving the coordination message.The operations of 1215 may be performed in accordance with examples asdisclosed herein. In some examples, aspects of the operations of 1215may be performed by a resource status component 830 as described withreference to FIG. 8 .

At 1220, the method may include identifying that a second communicationresource of a second unicast communication connection between the firstUE and the second UE is a non-preferred resource based on receiving thecoordination message for the first unicast communication connection thatindicates that the one or more communication resources are the preferredresources, the second communication resource corresponding to one of theone or more communication resources of the first unicast communicationconnection. The operations of 1220 may be performed in accordance withexamples as disclosed herein. In some examples, aspects of theoperations of 1220 may be performed by a resource status component 830as described with reference to FIG. 8 .

At 1225, the method may include selecting a communication resource forthe sidelink communications based on the identified status of the one ormore communication resources. The operations of 1225 may be performed inaccordance with examples as disclosed herein. In some examples, aspectsof the operations of 1225 may be performed by a scheduling component 835as described with reference to FIG. 8 .

The following provides an overview of aspects of the present disclosure:

Aspect 1: A method for wireless communications at a first UE,comprising: receiving, from a second UE, a coordination message over asidelink channel that indicates a preference status of communicationresources for sidelink communications between two or more UEs;identifying a status of one or more communication resources for thesidelink communications based at least in part on the receivedcoordination message, wherein the identified status of eachcommunication resource of the one or more communication resourcesindicates whether a respective communication resource is available,reserved, preferred, or non-preferred, or a combination thereof; andselecting a communication resource for the sidelink communications basedat least in part on the identified status of the one or morecommunication resources.

Aspect 2: The method of aspect 1, wherein identifying the status furthercomprises: identifying that the one or more communication resources arepreferred for the sidelink communications between the two or more UEs orthe one or more communication resources are non-preferred for thesidelink communications between the two or more UEs, wherein thepreference status indicates whether the one or more communicationresources are preferred or non-preferred for the sidelink communicationsbetween the two or more UEs.

Aspect 3: The method of any of aspects 1 through 2, further comprising:transmitting a message requesting the coordination message for thesidelink communications, wherein receiving the coordination message isbased at least in part on transmitting the message.

Aspect 4: The method of any of aspects 1 through 3, further comprising:identifying whether the first UE is an intended recipient of thecoordination message, wherein identifying the status of the one or morecommunication resources is based at least in part on identifying whetherthe first UE is the intended recipient of the coordination message.

Aspect 5: The method of aspect 4, further comprising: identifyingwhether the coordination message indicates preferred resources ornon-preferred resources, wherein identifying the status of the one ormore communication resources is based at least in part on identifyingwhether the first UE is the intended recipient of the coordinationmessage and identifying whether the coordination message indicates thepreferred resources or the non-preferred resources.

Aspect 6: The method of aspect 5, wherein identifying the status furthercomprises: identifying that the communication resource is a preferredresource based at least in part on the first UE being the intendedrecipient and the coordination message indicating the preferredresources.

Aspect 7: The method of any of aspects 5 through 6, wherein identifyingthe status further comprises: identifying that the communicationresource is a non-preferred resource based at least in part on a thirdUE being the intended recipient and the coordination message indicatingthe preferred resources.

Aspect 8: The method of any of aspects 5 through 7, wherein identifyingthe status further comprises: identifying that the communicationresource is a non-preferred resource based at least in part on the firstUE being the intended recipient and the coordination message indicatingthe non-preferred resources.

Aspect 9: The method of any of aspects 4 through 8, wherein thecoordination message includes or is associated with an indication of theintended recipient.

Aspect 10: The method of any of aspects 4 through 9, further comprising:identifying a destination identifier included in or associated with thecoordination message, wherein identifying whether the first UE is theintended recipient of the coordination message is based at least in parton identifying the destination identifier.

Aspect 11: The method of aspect 10, wherein the destination identifieris included in sidelink control information associated with thecoordination message.

Aspect 12: The method of any of aspects 4 through 11, whereinidentifying whether the first UE is the intended recipient of thecoordination message is based at least in part on the coordinationmessage being associated with a process to reserve the communicationresource for the sidelink communications.

Aspect 13: The method of any of aspects 1 through 12, wherein thecoordination message comprises a portion of an RRC message, a portion ofa MAC-CE, a portion of a first-stage SCI, or a portion of a second-stageSCI.

Aspect 14: The method of any of aspects 1 through 13, furthercomprising: the one or more communication resources for the sidelinkcommunications are associated with a first unicast communicationconnection between the first UE and the second UE; and identifying thestatus further comprises identifying that the one or more communicationresources are preferred resources of the first unicast communicationconnection based at least in part on receiving the coordination message.

Aspect 15: The method of aspect 14, further comprising: identifying thata second communication resource of a second unicast communicationconnection between the first UE and the second UE is a preferredresource based at least in part on receiving the coordination messagefor the first unicast communication connection, the second communicationresource corresponding to one of the one or more communication resourcesof the first unicast communication connection.

Aspect 16: The method of any of aspects 14 through 15, furthercomprising: identifying that a second communication resource of a secondunicast communication connection between the first UE and the second UEis a non-preferred resource based at least in part on receiving thecoordination message for the first unicast communication connection thatindicates that the one or more communication resources are the preferredresources, the second communication resource corresponding to one of theone or more communication resources of the first unicast communicationconnection.

Aspect 17: The method of any of aspects 14 through 16, furthercomprising: identifying that a second communication resource of a secondunicast communication connection between the first UE and a third UE isa non-preferred resource based at least in part on receiving thecoordination message for the first unicast communication connection thatindicates that the one or more communication resources are the preferredresources, the second communication resource corresponding to one of theone or more communication resources of the first unicast communicationconnection.

Aspect 18: The method of any of aspects 14 through 17, wherein thecoordination message indicates a source identifier and a destinationidentifier, the method further comprising: identifying the first unicastcommunication connection based at least in part on the source identifierand the destination identifier.

Aspect 19: The method of any of aspects 14 through 18, wherein thecoordination message includes a first indication of the first unicastcommunication connection and a second indication of a second unicastcommunication connection.

Aspect 20: The method of any of aspects 1 through 19, wherein thecoordination message indicates whether a resource conflict for the oneor more communication resources for the sidelink communications isdetected.

Aspect 21: The method of aspect 20, wherein an indication of theresource conflict comprises a NACK associated with a message transmittedby a scheduling UE of the sidelink communications.

Aspect 22: An apparatus for wireless communications at a first UE,comprising a processor; memory coupled with the processor; andinstructions stored in the memory and executable by the processor tocause the apparatus to perform a method of any of aspects 1 through 21.

Aspect 23: An apparatus for wireless communications at a first UE,comprising at least one means for performing a method of any of aspects1 through 21.

Aspect 24: A non-transitory computer-readable medium storing code forwireless communications at a first UE, the code comprising instructionsexecutable by a processor to perform a method of any of aspects 1through 21.

It should be noted that the methods described herein describe possibleimplementations, and that the operations and the steps may be rearrangedor otherwise modified and that other implementations are possible.Further, aspects from two or more of the methods may be combined.

Although aspects of an LTE, LTE-A, LTE-A Pro, or NR system may bedescribed for purposes of example, and LTE, LTE-A, LTE-A Pro, or NRterminology may be used in much of the description, the techniquesdescribed herein are applicable beyond LTE, LTE-A, LTE-A Pro, or NRnetworks. For example, the described techniques may be applicable tovarious other wireless communications systems such as Ultra MobileBroadband (UMB), Institute of Electrical and Electronics Engineers(IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, aswell as other systems and radio technologies not explicitly mentionedherein.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof.

The various illustrative blocks and components described in connectionwith the disclosure herein may be implemented or performed with ageneral-purpose processor, a DSP, an ASIC, a CPU, an FPGA or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described herein. A general-purpose processor may be amicroprocessor, but in the alternative, the processor may be anyprocessor, controller, microcontroller, or state machine. A processormay also be implemented as a combination of computing devices (e.g., acombination of a DSP and a microprocessor, multiple microprocessors, oneor more microprocessors in conjunction with a DSP core, or any othersuch configuration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described herein may be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations.

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that may beaccessed by a general-purpose or special-purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media mayinclude RAM, ROM, electrically erasable programmable ROM (EEPROM), flashmemory, compact disk (CD) ROM or other optical disk storage, magneticdisk storage or other magnetic storage devices, or any othernon-transitory medium that may be used to carry or store desired programcode means in the form of instructions or data structures and that maybe accessed by a general-purpose or special-purpose computer, or ageneral-purpose or special-purpose processor. Also, any connection isproperly termed a computer-readable medium. For example, if the softwareis transmitted from a website, server, or other remote source using acoaxial cable, fiber optic cable, twisted pair, digital subscriber line(DSL), or wireless technologies such as infrared, radio, and microwave,then the coaxial cable, fiber optic cable, twisted pair, DSL, orwireless technologies such as infrared, radio, and microwave areincluded in the definition of computer-readable medium. Disk and disc,as used herein, include CD, laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

As used herein, including in the claims, “or” as used in a list of items(e.g., a list of items prefaced by a phrase such as “at least one of” or“one or more of”) indicates an inclusive list such that, for example, alist of at least one of A, B, or C means A or B or C or AB or AC or BCor ABC (i.e., A and B and C). Also, as used herein, the phrase “basedon” shall not be construed as a reference to a closed set of conditions.For example, an example step that is described as “based on condition A”may be based on both a condition A and a condition B without departingfrom the scope of the present disclosure. In other words, as usedherein, the phrase “based on” shall be construed in the same manner asthe phrase “based at least in part on.”

The term “determine” or “determining” encompasses a wide variety ofactions and, therefore, “determining” can include calculating,computing, processing, deriving, investigating, looking up (such as vialooking up in a table, a database or another data structure),ascertaining and the like. Also, “determining” can include receiving(such as receiving information), accessing (such as accessing data in amemory) and the like. Also, “determining” can include resolving,selecting, choosing, establishing and other such similar actions.

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label, or othersubsequent reference label.

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “example” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details forthe purpose of providing an understanding of the described techniques.These techniques, however, may be practiced without these specificdetails. In some instances, known structures and devices are shown inblock diagram form in order to avoid obscuring the concepts of thedescribed examples.

The description herein is provided to enable a person having ordinaryskill in the art to make or use the disclosure. Various modifications tothe disclosure will be apparent to a person having ordinary skill in theart, and the generic principles defined herein may be applied to othervariations without departing from the scope of the disclosure. Thus, thedisclosure is not limited to the examples and designs described hereinbut is to be accorded the broadest scope consistent with the principlesand novel features disclosed herein.

What is claimed is:
 1. A method for wireless communications at a firstuser equipment (UE), comprising: receiving, from a second UE, acoordination message over a sidelink channel that indicates a preferencestatus of communication resources for sidelink communications betweentwo or more UEs; identifying whether the first UE is an intendedrecipient of the coordination message based at least in part onreceiving the coordination message; identifying a status of one or morecommunication resources for the sidelink communications based at leastin part on whether the first UE is the intended recipient of thecoordination message, wherein the identified status of eachcommunication resource of the one or more communication resourcesindicates whether a respective communication resource is preferred ornon-preferred; and selecting a communication resource for the sidelinkcommunications based at least in part on the identified status of theone or more communication resources.
 2. The method of claim 1, whereinidentifying the status further comprises: identifying that the one ormore communication resources are preferred for the sidelinkcommunications between the two or more UEs or the one or morecommunication resources are non-preferred for the sidelinkcommunications between the two or more UEs, wherein the preferencestatus indicates whether the one or more communication resources arepreferred or non-preferred for the sidelink communications between thetwo or more UEs.
 3. The method of claim 1, further comprising:transmitting a message requesting the coordination message for thesidelink communications, wherein receiving the coordination message isbased at least in part on transmitting the message.
 4. The method ofclaim 1, further comprising: identifying whether the coordinationmessage indicates preferred resources or non-preferred resources,wherein identifying the status of the one or more communicationresources is based at least in part on identifying whether the first UEis the intended recipient of the coordination message and identifyingwhether the coordination message indicates the preferred resources orthe non-preferred resources.
 5. The method of claim 4, whereinidentifying the status further comprises: identifying that thecommunication resource is a preferred resource based at least in part onthe first UE being the intended recipient and the coordination messageindicating the preferred resources.
 6. The method of claim 4, whereinidentifying the status further comprises: identifying that thecommunication resource is a non-preferred resource based at least inpart on the first UE being the intended recipient and the coordinationmessage indicating the non-preferred resources.
 7. The method of claim1, wherein the coordination message includes or is associated with anindication of the intended recipient.
 8. The method of claim 1, furthercomprising: identifying a destination identifier included in orassociated with the coordination message, wherein identifying whetherthe first UE is the intended recipient of the coordination message isbased at least in part on identifying the destination identifier.
 9. Themethod of claim 8, wherein the destination identifier is included insidelink control information associated with the coordination message.10. The method of claim 1, wherein identifying whether the first UE isthe intended recipient of the coordination message is based at least inpart on the coordination message being associated with a process toreserve the communication resource for the sidelink communications. 11.The method of claim 1, wherein the coordination message comprises aportion of a medium access control (MAC) control element (CE) or aportion of a second-stage SCI.
 12. The method of claim 1, wherein thecoordination message indicates whether a resource conflict for the oneor more communication resources for the sidelink communications isdetected.
 13. The method of claim 12, wherein an indication of theresource conflict comprises a negative acknowledgement (NACK) associatedwith a message transmitted by a scheduling UE of the sidelinkcommunications.
 14. An apparatus for wireless communications at a firstuser equipment (UE), comprising: a processor; memory coupled with theprocessor; and instructions stored in the memory and executable by theprocessor to cause the apparatus to: receive, from a second UE, acoordination message over a sidelink channel that indicates a preferencestatus of communication resources for sidelink communications betweentwo or more UEs; identify whether the first UE is an intended recipientof the coordination message based at least in part on receiving thecoordination message; identify a status of one or more communicationresources for the sidelink communications based at least in part onwhether the first UE is the intended recipient of the coordinationmessage, wherein the identified status of each communication resource ofthe one or more communication resources indicates whether a respectivecommunication resource is preferred or non-preferred; and select acommunication resource for the sidelink communications based at least inpart on the identified status of the one or more communicationresources.
 15. The apparatus of claim 14, wherein the instructions toidentify the status are further executable by the processor to cause theapparatus to: identify that the one or more communication resources arepreferred for the sidelink communications between the two or more UEs orthe one or more communication resources are non-preferred for thesidelink communications between the two or more UEs, wherein thepreference status indicates whether the one or more communicationresources are preferred or non-preferred for the sidelink communicationsbetween the two or more UEs.
 16. The apparatus of claim 14, wherein theinstructions are further executable by the processor to cause theapparatus to: transmit a message requesting the coordination message forthe sidelink communications, wherein receiving the coordination messageis based at least in part on transmitting the message.
 17. The apparatusof claim 14, wherein the instructions are further executable by theprocessor to cause the apparatus to: identify whether the coordinationmessage indicates preferred resources or non-preferred resources,wherein identifying the status of the one or more communicationresources is based at least in part on identifying whether the first UEis the intended recipient of the coordination message and identifyingwhether the coordination message indicates the preferred resources orthe non-preferred resources.
 18. The apparatus of claim 17, wherein theinstructions to identify the status are further executable by theprocessor to cause the apparatus to: identify that the communicationresource is a preferred resource based at least in part on the first UEbeing the intended recipient and the coordination message indicating thepreferred resources.
 19. The apparatus of claim 17, wherein theinstructions to identify the status are further executable by theprocessor to cause the apparatus to: identify that the communicationresource is a non-preferred resource based at least in part on the firstUE being the intended recipient and the coordination message indicatingthe non-preferred resources.
 20. The apparatus of claim 14, wherein thecoordination message includes or is associated with an indication of theintended recipient.
 21. The apparatus of claim 14, wherein theinstructions are further executable by the processor to cause theapparatus to: identify a destination identifier included in orassociated with the coordination message, wherein identifying whetherthe first UE is the intended recipient of the coordination message isbased at least in part on identifying the destination identifier. 22.The apparatus of claim 21, wherein the destination identifier isincluded in sidelink control information associated with thecoordination message.
 23. The apparatus of claim 14, wherein identifyingwhether the first UE is the intended recipient of the coordinationmessage is based at least in part on the coordination message beingassociated with a process to reserve the communication resource for thesidelink communications.
 24. The apparatus of claim 14, wherein thecoordination message comprises a portion of a medium access control(MAC) control element (CE) or a portion of a second-stage SCI.
 25. Theapparatus of claim 14, wherein the coordination message indicateswhether a resource conflict for the one or more communication resourcesfor the sidelink communications is detected.
 26. The apparatus of claim25, wherein an indication of the resource conflict comprises a negativeacknowledgement (NACK) associated with a message transmitted by ascheduling UE of the sidelink communications.
 27. An apparatus forwireless communications at a first user equipment (UE), comprising:means for receiving, from a second UE, a coordination message over asidelink channel that indicates a preference status of communicationresources for sidelink communications between two or more UEs; means foridentifying whether the first UE is an intended recipient of thecoordination message based at least in part on receiving thecoordination message; means for identifying a status of one or morecommunication resources for the sidelink communications based at leastin part on whether the first UE is the intended recipient of thecoordination message, wherein the identified status of eachcommunication resource of the one or more communication resourcesindicates whether a respective communication resource is preferred ornon-preferred; and means for selecting a communication resource for thesidelink communications based at least in part on the identified statusof the one or more communication resources.
 28. The apparatus of claim27, wherein the means for identifying the status further comprise: meansfor identifying that the one or more communication resources arepreferred for the sidelink communications between the two or more UEs orthe one or more communication resources are non-preferred for thesidelink communications between the two or more UEs, wherein thepreference status indicates whether the one or more communicationresources are preferred or non-preferred for the sidelink communicationsbetween the two or more UEs.
 29. A non-transitory computer-readablemedium storing code for wireless communications at a first userequipment (UE), the code comprising instructions executable by aprocessor to: receive, from a second UE, a coordination message over asidelink channel that indicates a preference status of communicationresources for sidelink communications between two or more UEs; identifywhether the first UE is an intended recipient of the coordinationmessage based at least in part on receiving the coordination message;identify a status of one or more communication resources for thesidelink communications based at least in part on whether the first UEis the intended recipient of the coordination message, wherein theidentified status of each communication resource of the one or morecommunication resources indicates whether a respective communicationresource is preferred or non-preferred; and select a communicationresource for the sidelink communications based at least in part on theidentified status of the one or more communication resources.
 30. Thenon-transitory computer-readable medium of claim 29, wherein theinstructions to identify the status are further executable by theprocessor to: identify that the one or more communication resources arepreferred for the sidelink communications between the two or more UEs orthe one or more communication resources are non-preferred for thesidelink communications between the two or more UEs, wherein thepreference status indicates whether the one or more communicationresources are preferred or non-preferred for the sidelink communicationsbetween the two or more UEs.